Jeremy Rayner has written a groovy-mode for emacs, details of which can be found on the Emacs Plugin page.
Russel Winder has started an alternative to Jeremy's based on CC Mode (Jeremy's was reworking of ruby-mode). Also Stuart Clayman has created a Groovy execution mode. See the Emacs Plugin page for See the Emacs Mode page for further details.
Find more info on the UltraEdit Plugin page.