{RubyChatter} Awesome site for trying out (or learning) Ruby: tryruby.

You can try out Ruby without installing it! Also, there is a 20 minute tutorial on this site which you could learn basic stuff about Ruby. One glitch is that you can't erase what you wrote so you have to start over again if you make a typo.
RATING: 4/5
LINK: TryRuby
SCREENSHOT: 

Sincerely yours, 
Admin