Geoffrey Tien has released the first version of his project for the GP2X:
A 2D scrolling shooter in the "manic bullet curtain" style. Please see the readme file included in the game download for more details, or grab the (incomplete) readme here.
The game is written in C++ and uses a special SDL library for GP2X.
This is currently a work-in-progress, estimated at approximately 30% completion as of July 1, 2006. Screenshots of an early build can be found below.
More info --> http://members.shaw.ca/gctien/gp2xdev/gp2xdev.html