Here’s a running list of apps from the Chrome Web Store that can help you develop on your Chromebook or Chromium OS device:

Chrome Dev Editor (Developer Preview) - Editor for building Web Apps and Chrome Apps, in JavaScript or Dart. CDE also supports Git and Polymer development.

https://chrome.google.com/webstore/detail/chrome-dev-editor-develop/pnoffddplpippgcfjdhbmhkofpnaalpg

Secure Shell - Terminal emulator and SSH client

https://chrome.google.com/webstore/detail/secure-shell/pnhechapfaindjhompbnflcldabbghjo

Chrome Remote Desktop - Access other computers or allow another user to access your computer securely over the Internet

https://chrome.google.com/webstore/detail/chrome-remote-desktop/gbchcmhmhahfdphkhkmpfmihenigjmpp

Text - A basic text editor for Chrome OS and Chrome

https://chrome.google.com/webstore/detail/text/mmfbcljfglbokpmkimbfghdkjmjhdgbg

Beagle Term - Terminal emulator with serial port through USB dongles

https://chrome.google.com/webstore/detail/beagle-term/gkdofhllgfohlddimiiildbgoggdpoea

Cloud9 - an online platform for development that makes developing applications more convenient than ever

https://chrome.google.com/webstore/detail/cloud9/nbdmccoknlfggadpfkmcpnamfnbkmkcp

Runnable - Cloud-based IDE

http://runnable.com/

To test your Android apps on Chrome OS, learn how to sideload Android apps on your Chromebook