Free tier: unlimited public and private repositories for 5 users, 1GB storage/repository, 1GB file storage, 50 minutes build time/month
Pros: provide pull requests, issue tracking, code snippets and wiki, has a desktop app

Cloud9

Free tier: unlimited public workspace and 1 private workspace, 1 CPU, 512MB RAM & 2GB HDD per workspace
Pros: supports PHP, Node.js, Django, Ruby on Rails with MongoDB and MySQL database, can also choose basic Ubuntu installation
Limitations: runs on the AWS EC2 Free Tier; so shares the EC2 limitation of expiry after 12 months.

Codeanywhere

Free tier: Web-based IDE accessible from desktop or mobile device, unlimited live collaboration, 1 revision per file, 1 remote connection (FTP, virtual machine, cloud provider), 1 custom domain, 1 container with 256MB of RAM and 2GB storage
Pros: available from everywhere, allows live collaboration on code
Exceeding the free tier: If you attempt to create more than 1 GitHub connection, for example, it will block it and suggest you pay for Codeanywhere.

Free tier: unlimited public repositories with unlimited collaborators and organizations. Unlimited private repositories with up to 3 collaborators
Pros: provide issue tracking, code snippets (Gist), code reviews, wiki, organizations/team management, 3rd party integration and hooks, has a desktop app

Free tier: unlimited public/private projects, unlimited private collaborators, unlimited global storage, 10GB storage/project
Pros: provide issue tracking, code snippets, wiki and webhooks, can be also self hosted by downloading GitLab Community Edition, provide also free continuous integration services for GitLab.com users (on shared runners, see GitLab CI)

Free tier: unlimited code hosting with Bazaar, free for Open Source
Pros: bug tracker, code review tool, community translations collaboration, building and hosting Ubuntu packages, mailing lists, simple project specification tracker