BTW, i wanna suggest you - advanced coders - an old but very fan free DOS multiplayer game Jump'n'Bump. Unfortunately, it doesn't run on PSP-DosBox (crashes with the BUS Error), but source code is avaluable: http://jumpbump.mine.nu/ and, as you see there, it has alredy been ported to lots of platforms (Win, Linux, MacOS, FreeBSD, GP2X, XBOX, PlayStation 2...) Ша you haven't played it yet, just try with a friend!
The game is really very simple: only one game screen, simple game mechanics/animations, so i think, porting it to psp won't be a challenge...
![Image](http://img157.imageshack.us/img157/236/jumppo7.jpg)
It would be also groovy, if such PSP-port suppoted Ad-Hock/Infrastructure multiplayer for 2-4 players + 2 player MP on a single PSP (only 3 buttons are required for each player!) + sp against bots; customisable player skins/game screen and something like a "level" editor (the game alredy has the ability to create levels and the huge levelmaking tutorial, but some app with GUI might be better)...