Can you use a ps2 controller on a psp?

So far no can do, Sony is probably not going to integrate such a feature since the PS3 has more buttons and includes the motion sensor.

yes you can but u need wireless conect

The PSP can be used in place of a PlayStation 3 controller under certain circumstances. The most notable example of this is Remote Play; in this mode, the PSP connects to the PS3 either through a wireless internet connection or directly with Wi-Fi between the PS3 and PSP. Using Remote Play, the user can access a majority of the PS3's features on the PSP, including but not limited to image viewing and internet browsing. Some games also support the PSP as a PS3 controller, such as Lair. Furthermore, if a PlayStation 1 game is inserted in the PS3, it can be played through the use of a PSP while in Remote Play mode. Remote Play can also be set so that the PSP can remotely turn the PS3 on and off, although in this setting, the PS3's fan and Wi-Fi will remain active even when the system is not in use.