Sure, the DesMuME PSP emulator's compatibility record is spotty at best and its author, Sektor, claims that the software runs at about three frames per second at 333 MHz, but it's running Nintendo DS software on a PSP. That has to count for something, right? That something is probably nothing more than "Look what I did!" as the emulator "will never be full speed" and most likely never functional for practical game playing purposes. But, look! DS games running on a PSP!
My suggestion for playing DS titles on your PSP is shown in the thumbnail picture above. E-mail me for instructions.
DesMuME PSP Unofficial Useless Edition - Nintendo DS Emulator for the PSP [DC Emu PSP News, thanks Wraggy!]