We have done some preliminary J2ME development of an app on iPaq and
found it to be quite acceptable (compared to some phone devices). The
good thing is that iPaq and Sharp Zaurus share the same Java VM
implementation (Jeode) so apps should run on both environments.
I bought the book Java Development on PDAs: Building Applications for
Pocket PC and Palm Devices by Daryl Wilding-McBride (Author) and found
it a good base - quite a thin book but it gives you the basics specific
for the PDA environment. There is plenty of general resources on J2ME
and Personal Java Profile around.
http://www.javaonpdas.com/ Check amazon.com or your bookshop.
If you find additonal resources I'd appreciate if you could forward.
HTH,