Video: PS2 Controller Hacked, Used to Control PSP Console
Recently http://tokyodriftpsp.wordpress.com/projects/ps2-controller/ hacked a PlayStation 2 controller and built an adapter that allows you to connect the PS2 gamepad to a Sony PSP console to control it.
For those curious, this adapter didn't require any hardware alteration to the PSP or the PS2 controller, as a plug-in was used on the PSP Firmware side of things.
The adapter then makes use of video out and PS2 controller extension cables, along with an ATmega8 microcontroller to handle the signals between the two devices.
Check out a video of the PS2 controller hack in action with a PlayStation Portable below, via YouTube!
i think you can already use your PS3 controller if you have a PSP Go. you can use your PS3 controller to wirelessly control your PSP Go via bluetooth connection on your PSP Go. Only PSP Go has bluetooth connection, all older PSP models have only WiFi.