Here is a round up of some PlayStation Portable open source games Team Sushi has made using the open source toolkit by http://www.ps2dev.org/ and friends.
PSP Connect 4 (November 2006)
Connect 4 for the PlayStation Portable. pc4-1_1.zip (4MB)
PSP Wolfenstein 3D (November 2006)
There are better ports of Wolfenstein now, but AFAIK mine was first, and at least some of the others were improvements derived on my version.
Full details at http://www.adamcon.org/~dmwick/psp/wolf3d.html
Gunnar Hero (August 2007)
Download Gunnar Hero at QJ
Sushi Rubik (November 2007)
Check out my submission to Neo Flash compo 2008.
Resonate (June 2008)
Inspired by the abstract PS2 game Rez.
Download resonate version 0.57 (4740k)
See also Hardhat’s PSP Homepage