The Neo flash team who are already known for their DS flash carts have announced that they are working on a Memory Card converter for the PSP, heres the info posted:
NEO-MS converter SPEC:
1. Support SD / MMC / CF , up to 32GB.
2. Read / Write files through PSP link to PC USB port directly, not need the extra USB loader.
3. Support ALL MP3 / MP4 / UMD Movice / EMU / ISO ..... everything.