It's a simple enough little piece of software, with tools for synchronising content with your desktop PC and down converting video files to display on the PSP's screen (yes, it even does wide-screen). It'll even sync iTunes and browser favourites (it still doesn't take OPML and fill out the PSP's RSS reader, but that's still new enough that they haven't had time to write the code...)
Well worth registering at only $15. It's given me a whole new place to watch my fansubs!
Mac and Windows versions available.
Thanks to codepope for the recommendation