Here is a web based Groovy console, so the next time you are say on the train and want to write some Groovy using your iPhone* or at some PC with a locked down environment, you can!
http://groovyconsole.appspot.com/
Hours of fun or your money back :-p
* Nope, never wanted to write Groovy on the train either, but you never know.
Update from a former colleague of mine:
BTW, this is hosted on Google App engine, which only recently started supporting Java! There still seem to be some issues, I can’t execute code like System.properties{e,k->println e} due to some security exceptions. Similalry File based code also seems to be violating some google App Engin security.