Next Monday (estimated release date), there will be a new article on Gamasutra titled 'Cross-platform development of games for mobile devices'. The accompanying library has been added to SourceForge, the project is named 'MobileCore'.
MobileCore is a very small library that sits between the hardware (and libraries that sit directly on top of the hardware, like GAPI or PocketHAL) and the game application. It lets you develop games once, and compile them for many platforms. Right now MobileCore supports PocketPC and Symbian (and of course Win9x for easy 'emulation'). It abstracts the application entry point, display, buttons, stylus and sound system for the supported devices. More platforms can easily be added; a platform expert should be able to add support in a day. I am hoping that the Zodiac, GP32 and Tungsten-T will join in soon, as these devices have similar characteristics (as PPC & Symbian). MobileCore is thus NOT a game library; it's more 'EasyCE' for multiple platforms; game libraries could be build on top of this thing.
I hope this will help to get a broader audience for mobile games, and that it will free us all of the platform details that get in the way of cool game coding.
Check it out at http://www.sourceforge.net/mobilecore .
You'll want to read the article before diving in too deep; there's no documentation yet (although using it is not exactly rocket science).
The article is out early next week, but you heard it right here first.

Greets
Jacco.