I usually don’t get to run PSP hacks as features because everyone else snatches them up so quick (Is anybody actually buying games?). XyTec found this hack to connect multiple controllers to the PSP. The project uses an ATMega8 microcontroller to monitor the controller’s state and then transmits that to the PSP’s IrDA port. There is a nice discussion of how the communication works. There’s a video demo of the controller being used to play Doom also. The project isn’t quite finished, but it does include source. Time for some two-player emulation.