PSP-Hacks.com

Complete all-in-one firmware packages

Hacked or better known as, "custom firmwares." Including those by Dark_AleX.

Official PSP System Software Updates

Firmware downgraders

A large selection of plug-ins for custom firmwares.

DevHook releases, MPH Firmware Launchers, easy-to-use installers

Firmware Dumps

Tools to dump & decrypt various firmware versions

Homebrew apps to alter firmware behaviour -- X-Flash, Wave Flasher, TIFF Font Hacker, and more...

Easy PSP Upgrader/Downgrader

How to downgrade your PSP.