Codestation has released a nice plugin called, Game Categories Lite, now is v1.2.
This plugin is based on the same source code from Game Categories Revised v12 and Game Categories Light 1.3 which made by Bubbletune,
and now compatible with both 6.20 & 6.3X Custom Firmware.
Taken from Readme.txt:
Changelog:I changed the name of the project (doing a fork in the process) to avoid confusion
with GCL (this plugin doesn't use the folder categories present in firmwares 6.xx)
and GCR (the plugin is based heavily in GCL since it doesn't use a kernel/user approach).
To create categories just make a directory called CAT_<name_of_the_category> in the
/PSP/GAME folder, you can also create categories inside /ISO and they are going to be
merged with the one in /PSP/GAME (if the category exists).
To hide the "Uncategorized" category create a file named hide_uncategorized.txt and
place in the /SEPLUGINS directory.
You can get the source code from https://github.com/codestation/gclite
[!]Fixed PSPGo categories, again (thx RUSTII for the tests, again)
[!]Fixed the free space display when the psp returns from sleep
[!] Fixed PSPGo categories (thx RUSTII for the tests) - BROKEN
* Restore support for contextual categories (from GCR v12).
* Add option to use the categories "new" format (without CAT_ prefix).
* Restore options menu.
Please help me to get more space on my DropBox account and register here for free and get also 2gb space! So I don't need to upload files more on mu etc.