Update #3: The author has now released PSP UAE v0.31. Changes and updates include the Chip memory being set to 2MB so Monkey Island works (again), File selector improvements, and the addition of an options menu.
Update #2:PSP UAE v0.3 has been released, with changes including the addition of both menu and disk selection, a new icon and background image, and lastly you can now install PSPUAE in any PSP/GAME folder.
Update:PSP UAE v0.2 has now been released, with changes including the addition of preliminary sound support and auto-framerate functionality. A UAE File Selector has also been released as well for use with it.
Today Fcorbier has released PSP UAE v0.1, a port of the http://www.freiburg.linux.de/~uae/ Amiga Emulator for PSP! It runs at about 75-80% of a real Amiga 500 speed, but some games are definitely playable such as E-Motion and Rick Dangerous. The source code is included, and future versions may include such features as a menu, sound, disk selection, and keyboard emulation. Cool stuff!