Squeak may not be available but there is Pocket Smalltalk (PocketST) at
http://www.tiac.net/users/ajb/pocketst/index.html.
It only runs on Windoze95 at my last look.
This is a Smalltalk development environment which will create .PRC files
which then run under PalmOS.
You should check out the 3Com site for other tools as well, in
particular the emulator which allows you to test you apps without
downloading to the Pilot.
PocketSt is truly a step in the right direction for Pilot development.
H.E.Fassl
hefassl at mcs.net