I've been looking into this as well and I found this...

J2ME

It's Java mobile edition. It's all free (whoo hoo!) and there's a lot of documentation and samples. Hope it helps.

Java development is great as it's more or less portable. However it's still slow & you're basically restricted to 2d stuff. Although there's a pretty decent Java wolfenstein clone! I found a demo somewhere of both of those, and the hudson blade one can be *cough* decompiled & edited a wee bit to let you play the entire first level rather than quitting after 30 seconds. It's still only got one level but gives you a better chance to enjoy it. Before anyone comes down on me for this, I didn't steal it, the code is still obfuscated, and I bought the full game anyway cos it's pretty cool imho.
But that said if you don't want people doing this to your products then don't use java.

I've been playing with Symbian development (Cpp) on my nokia. Sadly most SDKs are not cross platform, except for within the same manufacturer. And then there are all kinds of different versions of SDK depending on which model you're targetting.. Apart from that if you've got a nokia smartphone head over to forum.nokia.com (although I've noticed it's down at the moment) I don't know about other manufacturers but I think eriksson have a similar site. Alternatively you can use BREW but I have no idea about that.

The Nokia SDKs come with all the tools you need to compile & package your programs, as well as an emulator for a particular device. Nokia are very good at providing sample apps as well, and the documentation is pretty decent. To upload them you may need a separate (but also free) program for your particular phone, also available off their site.

Also you can program in OpenGL ES on series 60 devices upwards with the hybrid implementation although it's not free for anything other than learning. There's another in the works called Vincent although support for phones wasn't great last time I checked, it's getting there though and more importantly it's open source.
Newer phones support GL ES without needing third party libraries, but for older phones (mines a 6600) the libraries work fine.

As for IDEs, Eclipse is a good (and free) one to use.

Finally if you click on only one of these links, NewLC.com is where you want to be headed for some pretty good tutorials. Setting up eclipse for use with symbian is one such example.

And now you know more or less as much as me.

edit: Oh yeah there's also a book on OpenGL ES - OpenGL ES Game Development, however I had to import it from the US & it's not all that great - largely one big advert for BREW. There are a few useful tidbits in there about phone development in general though, but really not worth the cash.

double edit: Also as most symbian sdks use gcc as a compiler, there's a project with different versions which report slight increases in performance, although are not always as compatible. I've had no problems with any of them though. Link

[Edited by - DrewGreen on September 4, 2005 8:19:23 PM]