PSX2PSP will convert .bins to compressed .pbp files if you want single file games that the Mednafen core can load. Beware though; a few games can freeze in .pbp format (Wipeout games, Diablo).
… I did NOT know this… dangit. So much for it being a perfect compression solution. I may not even bother with compression and just delete some of the crap games from the library.