LucidEngine is a simple layer over MIDP compatible phones that will let you write simple and old fashioned games using a specific language.
Every game you'll develop will basically work on all the devices (even not phones) LucidEngine as been ported.
Award winning commercial game Bomber for Nokia Series 60 is now available for free complete with full source code (J2ME).
Fly WWI plane in world with realistic physics, destructable terrain and other goodies.