This PSP emulator for Android actually works (kind of)
Some titles, however, are considered playable, according to the developer of PPSSPP. Puzzle Bobble Deluxe and Pinball Fantasies can be played, as long as you don't mind the glitches that are yet to be ironed out. 3D games are also mostly a no-go, and the great majority of other titles will not take you much further than their main screen.
Still, if you are a die-hard PSP fan, keep an eye out for more reliable versions of PPSSPP. Also, you can grab version 0.2 of the emulator from the Play store and give it a try. ROMs, however, you'll have to find yourself.
source: PPSSPP, Android Market link