There is a new project at Kenai:
NBAppEngine.
As the name suggests, this is intended to provide a
NetBeans
plugin for the Google AppEngine.
Check the introductory writeups by
Petr
and
Geertjan;
check it out,
and consider helping out.

On a related topic, I noticed that
Mojarra 1.2.13
now has “support” for Google AppEngine;
see
ChangeLog.