SuperFury has released an update to POPStation PSP -- a homebrew app that converts any PSX game to a compatible POPs format, meaning you can play said PSX (or PS1 / PSOne) game on your hacked or homebrew-enabled PSP.
If you're not familiar with POPStation PSP, then I suggest you read over the included readme.txt to get started.
And for POPS itself, weed through these posts to find the version appropriate for your CFW/HEN ... or use neur0n's PopsLoader Bridge if you're running CFW ME.