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! Currently the PRO-B9 CFW is in BETA stage, use at own risk!

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/