Here's PSPosx 0.1a BETA which was originally released back in March of 2006.
It's basically a shell which allows the user to view images,
listen to their favourite mp3s, run homebrew, and much much more.
This is basically a generic flasher which can flash whatever files your heart desires. I've tried to make the process as simple and noob friendly as possible.
You can flash anything from individual files neatly organized as you wish, all the way up to entire themes also organized as you wish. You can also save precious flash space for themes with the click of a button - backing up your files as well.
The customizations available to your PSP are endless.
And here's a theme pack I've created for Slash-N-Flash. These themes are meant for 3.52 M33 ONLY.