I while ago I discovered a way to get Wolfenstein 3D onto a PSP that's using custom firmware. I found a port which uses the same VGA, audio, and gamemap files as the PC version. The port is merely the Wolf3d and Spear Of Destiny engines compiled into a PSP eboot, so you'd need the original Wolf3d or Spear Of Destiny files to play on PSP.
But if you're copying the VGA, audio, and gamemap files, can't mods work too? Yes, however many Wolf3d mods use modified engines so the gameplay won't be dead on as playing the mods on the PC. Unfortunatley, the more awesome mods like Spear Resurrection, MedEvil, Femstein, none of them will work... However I've been toying around and am currently taking a break from Insanitarium to create a mod that uses the original Wolf3d engine and IS entirely playable on Playstation Portables! It is called BioWeapon, and is inspired mostly from Resident Evil and Quake II.
Working on BioWeapon gets kinda boring though, the overall feel is just like classic Wolf3d just with new graphics, levels, music and sound. But still, the idea itself is awesome: The 1st ever Wolf3d mod specifically designed to be played on the go!