PSP homebrew developer Bubbletune has released a new version of the Game Categories plugin. Just like the name says, this plugin lets you categorize and organize your PSP's Game menu.
Version 3 has only one new feature: added support for the recently-released custom firmware 5.00 M33-4. According to the dev, "due to the new Shutdown option being added, a lot of offsets changed."
This plugin requires a PSP running custom firmware 5.00 M33-3 or M33-4. Check out the readme file included in the download for installation instructions.