The GP32 is a hand-held console created by a Korean company called GamePark. It attracts a lot of homebrew hacker interest, as the SDK is freely available and it is easy to get up and running with the hardware. That gorgeous, huge 320x240 screen is just a big block of memory waiting to be filled with pixels!
Some useful links to learn more:
[ GP32X ] [ GP32 Emu ] [ GP32 Dev'rs ] [ Mr. Spiv ] [ Darkfader ]

If you're so inclined, you can probably find one to purchase off EBay, or off gp2x. The GP32 has recently been superseded by the GP2X - a similarly awesome bit of kit, Two 200mhz CPU's with 64meg of RAM, custom graphics hardware and decoding chips.
Xenon 2 running on the CaSTaway Atari ST emulator,
on the GeePee32 GP32 emulator. Just one of the many
emulators available...
While cobbling some stuff together for my GP32 I ended up writing a bunch of tools for it to make development quicker and smarter. The two principle projects have their own pages - GP32 Generator for Metrowerks Codewarrior and the GP32USB library.
I got half way through developing a re-make of Paradroid for the GP32 too - the level authoring tools I wrote for that are available in the C# section.