I am a Ruby on Rails developer and I have been developing on my Chromebook (and any place with a browser) using Nitrous.io (https://www.nitrous.io/). There are also other comparable services as well. I mainly use it on days when I am working from home. It give me terminal access in the browser, (but not quite full sudo) as well as a decent IDE.

I have yet to use Crouton on my Chromebook because I have another laptop running Ubuntu and I just haven't found the need yet (though to be honest I haven't picked up my old laptop since I got the Chromebook).

Browserstack lets me check out what the web pages look like in other browsers.

If you do use Crouton, then you should basically have a Ubuntu box. Most Chromebooks have an SD Card slot and USB slots as well if you need extra storage.