Upcase by thoughtbot - An online learning platform for developers - now free
Anima App - Design, get feedback, convert to code, publish, iterate.
PracticeLinux - Learn Linux, Vim, Git, Tmux, Gpg and more
Sketch Repo - Collection of resources for anyone who uses Sketch
Enbitious - An online business learning marketplace that helps all ambitious entrepreneurs to learn & network.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.