The “PRO” CFW for PSP claims to be “most compatible Aftermarket Custom Firmware”. Please be aware that modifying your Firmware might brick your PSP and will break you warranty!

Features:

* Homebrew Compatible – Run your own unsigned applications, both user and kernel mode.
* Plugin Compatible – Add new features to your PSP via kernel mode background plugins.
* ISO / CSO Game Dump Playback – Backup your own UMD discs via USB and play them from Flash Storage.
* 2g+ Memory Range Unlock – Use the previously locked RAM range within your own homebrews.
* NODRM Engine – Use your bought DLCs, no matter on which PSN account you are currently logged in.
* PSX Emulator Unlock – Play your PSX classics, yes – all of them. Not just PSN titles.
* And a lot more…

http://code.google.com/p/procfw/