Developers and Open Source authors now have a massive amount of services offering free tiers, but it can be hard to find them all in order to make informed decisions.
The scope of this particular list is limited to things infrastructure developers (System Administrator, DevOps Practitioners, etc.) are likely to find useful. We love all the free services out there, but it would be good to keep it on topic. It's a bit of a grey line at times so this is a bit opinionated; do not be offended if I do not accept your contribution.
You can help by sending Pull Requests to add more services. Once I have a good set of links in this README file, I'll look into a better layout for the information and links (help with that is appreciated too).
* https://www.wunderlist.com/ - Share your lists and work collaboratively on projects with your colleagues - Available for free to download and use on iPhone,iPad,Mac,Android,Windows and the Web.
* http://sematext.com/spm - Free for 24h metrics, unlimited number of servers, 10 custom metrics, 500K custom metrics data points, unlimited dashboards, users, etc.
* https://sealion.com/ - Free up to 2 servers, 3 days data retention, graphs and raw command output history (`top`, `ps`, `ifconfig`, `netstat`, `iostat`, `free`, custom, etc.)
* https://www.stathat.com/ - Get started with ten stats for free, no expiration.
* https://www.skylight.io/ - Free for first 100k requests
* https://www.appdynamics.com/ - Free for 24h metrics, application performance management agents limited to one Java, one .NET, one PHP, and one Node.js
* https://deadmanssnitch.com/ - Monitoring for cron jobs. 1 free snitch (monitor) - more available if you refer others to sign up
* https://www.algolia.com/ - Hosted search-as-you-type (instant). Free hacker plan up to 1,000 documents and 50,000 operations. Bigger free plans available for community/open source projects.
* https://swiftype.com/ - hosted search solution (API and crawler). Free for a single search engine with up to 1000 documents. Free upgrade to Premium level for open-source projects.
* https://bonsai.io/ - Free 1GB memory and 1GB storage.
* http://www.searchly.com/ - Free 2 Indices and 5MB storage.
* http://sendgrid.com/ - 400 emails per day for free/25,000 free transactional emails per month for emails sent from a Google compute instance or Microsoft Azure App Service
* https://developers.google.com/speed/libraries/ - The Google Hosted Libraries is a content distribution network for the most popular, open-source JavaScript libraries.
* https://www.asp.net/ajax/cdn - The Microsoft Ajax Content Delivery Network (CDN) hosts popular third party JavaScript libraries such as jQuery and enables you to easily add them to your Web application
* http://restlet.com/products/apispark/ - APISpark enables any API, application or data owner to become an API provider in minutes via an intuitive browser interface.
* https://www.firebase.com/ - Build realtime apps, free plan has 50 Max Connections, 5 GB Data Transfer, 100 MB Data Storage. 1 GB Hosting Storage and 100 GB Hosting Transfer.
* https://www.openshift.com/ - Red Hat PaaS, free tier provides three small gears (each with 512MB memory, 1GB storage). {[Browse one-click deployments](https://hub.openshift.com/)}.
* https://www.activestate.com/stackato/ - Enterprise-hardened Cloud Foundry PaaS from ActiveState, for private, public and hybrid cloud, free up to 20GB
* http://www.outsystems.com/ - Enterprise web development PaaS for on-premise or cloud, free "personal environment" offering allows for unlimited code and up to 1GB database.
* https://platform.telerik.com/ - Build and deploy mobile applications using Javascript. Free plan has 100 MB Data Storage, 1GB File storage, 5GB Bandwidth, 1 million push notifications for BaaS offering, 100 active devices for analytics.
* http://scn.sap.com/docs/DOC-56411 - The in-memory Platform-as-a-Service offering from SAP. Free developer accounts come with 1GB structured, 1GB unstructured, 1GB of Git data and allow you to run HTML5, Java and HANA XS apps.
* https://www.mendix.com/ - Rapid Application Development for Enterprises - Unlimited number of free sandbox environments supporting 10 users, 100MB of files and 100MB database storage each.
* https://www.tutum.co/ - The Docker Platform for Dev and Ops - Build, deploy, and manage your apps across any cloud - free while in beta and free developer plan when tutum will be production ready
* http://apigee.com/docs/api-baas (product docs), http://apigee.com/docs/developer-vs-edge (registration) - Unlimited trial includes NoSQL data store with 25GB of storage, user and permission management, geolocation, 10,000,000 push notifications per month, remote configuration, beta and A/B split testing, APM, fully API driven. Accessible and manageable via UI, SDK, and API.
* https://bip.io/ - A web-automation platform for easily connecting web services. Fully open GPLv3 to power the backend of your open-source project. Commercial OEM License available.
* https://www.contentful.com/ - Content as a Service. Content Management & Delivery APIs in the cloud. 3 users, 3 spaces (repositories) and 1,000,000 API requests per month for free.
* http://www.kinvey.com/ - Mobile backend, starter plan has unlimited requests per second, with 2 GB of data storage, as well as push notifications for up 5,000,000 unique recipients. Enterprise application support.
* https://www.parse.com/ - Mobile backends, free plan has 30 requests per second, with 20 GB of file and database storage, as well as push notifications for up to 1,000,000 unique recipients.
* http://www.dreamfactory.com/ - DreamFactory is an open source backend platform that provides all of the RESTful services you need to build fantastic mobile and web applications
* https://www.mashape.com/ - API Marketplace And Powerful Tools For Private And Public APIs. With the free tier, some features are limited such as monitoring, alerting and support.
* https://www.simplybuilt.com/ - SimplyBuilt offers free website building and hosting for open source projects (http://www.simplybuilt.com/explore/free-websites-for-open-source-projects). Simple alternative to GitHub Pages.
* http://www.devport.co/ - Turn GitHub projects, Apps, and websites into a personal developer portfolio.
* https://www.netlify.com/ - Builds, deploy and hosts static site or app, free for 100 MB data and 1 GB bandwidth.
* https://www.acquia.com/free - Hosting for Drupal sites. Free tier for developers. Free development tools (such as Acquia Dev Desktop) also available.
* https://kimonolabs.com/ - "Turn websites into structured APIs from your browser in seconds", free for public APIs, up to 20 million pages fetch / month. Supports scheduling, JSON, CSV, post-auth, ...
* https://www.cloudamqp.com/ - RabbitMQ as a Service. Little Lemur plan: max 1M message per month, max 20 concurrent connections, max 100 queues, max 10,000 queued messages, multiple nodes in differen AZ's.
* https://www.visualstudio.com/products/what-is-visual-studio-online-vs - Unlimited free private code repositories; Tracks bugs, work items, feedback and more.
* http://www.targetprocess.com/ - Visual project management, from Kanban and Scrum to almost any operational process. Free for unlimited users, up to 1000 data entities (more details at http://www.targetprocess.com/pricing/).
* http://cloudinary.com/ - Image upload, powerful manipulations, storage, and delivery for sites and apps, with libraries for Ruby, Python, Java, PHP, Objective-C and more. Perpetual free tier includes 7500 images/month, 2gb storage, 5gb bandwidth.
* https://plot.ly/ - graph and share your data. Free tier includes unlimited public files and 10 private files.
* https://transloadit.com/ - Handles file uploads & encoding of video, audio, images, documents. Free for open source & other do-gooders. Commercial applications get the first GB free for test driving.
* http://embed.ly/ - Provides APIs for embeding media in a webpage, Responsive image Scaling, Extracting elements from a webpage. Free for up to 5,000 URLs per Month at 15 Requests per Second
* https://c9.io/ - IDE in a browser. Incorporates an Ubuntu virtual machine and in-browser terminal access. Integrates with github and bitbucket, but also adds SFTP and generic Git access.
* https://codeanywhere.com/ - Full IDE in the browser and mobile apps. Access FTP, SFTP, Dropbox, Google Drive, GitHub, and BitBucket. Hosted virtual machines with terminal access. Collaboration features like share links, live editing, permissions, and version tracking.
* https://codenvy.com/ - IDE and automated developer workspaces in a browser, collaborative, git/SVN integration, build and run your app in customizable Docker-based runners (free tier includes: 4GB RAM, always-on machines, ability to run multiple machines simultaneously), pre-integrated deploy to Google Apps.
* https://koding.com/ - IDE in a browser. Features: Full sudo access - VMs hosted on Amazon EC2 - SSH Access - Real EC2 VM, no LXCs/hypervising - Custom sub-domains - Publicly accessible IP - Ubuntu 14.04 - IDE/Terminal/Collaboration
* https://www.nitrous.io/ - Private Linux instance(s) with interactive collaboration, free for 2 hours a day. {[More Details](http://goo.gl/J1Zbsg)}
* http://visualstudio.com/free - Fully-featured IDE with thousands of extensions, cross-platform app development (Microsoft extensions available for download for iOS and Android), desktop, web and cloud development, multi-language support (C#, C++, JavaScript, Python, PHP and more).
* https://apiary.io/ - Collaborative design API with instant API mock and generated documentation (Free for unlimited API blueprints and unlimited user with one admin account and hosted documentation)
* https://www.mockable.io/ - Mockable is a simple configurable service to mock out RESTful API or SOAP web-services. This online service allows you to quickly define REST API or SOAP endpoints and have them return JSON or XML data.
* https://www.jetbrains.com/products.html - Productivity tools, IDEs and deploy tools. Free license for students, teachers, open source projects, and user groups.
* https://www.sourcelair.com/ - In-browser IDE for Django, JavaScript, HTML5, Python, and more. Integrates with Git, Mercurial, GitHub, Heroku and more. Free forever for 1 private project.
* https://www.cognalys.com/ - Freemium mobile number verification through an innovative and reliable method than using SMS gateway. Free accounts will have 70 Tries and 50 verifications per day. {[Signup](https://www.cognalys.com/signup/1)}
* https://www.braintreepayments.com/ - Credit Card, Paypal, Venmo, Bitcoin, Apple Pay (, ...) integration. Single and Recurrent Payments. First $50 are free of charge.
* http://taxratesapi.avalara.com/ - Get the right sales tax rates to charge for the close to 10,000 sales tax jurisdictions in the USA. Free REST API. Registration required.
* https://www.tutum.co/ - The Docker Platform for Dev and Ops - Build, deploy, and manage your apps across any cloud - free while in beta and free developer plan when tutum will be production ready
* https://www.fullcontact.com/developer/pricing/ - Help your users know more about their contacts by adding social profile into your app. 500 free Person API matches per month.