Logitech Playgear Amp
Amazon.com: PSP PlayGear Amp: Video Games
Has clip to hold psp between speakers made for phat but slim sits there fine.
Pick up the last set on sale at Gamestop for 9.99 originally 39.99.
They are AMAZING, so much louder and clearer then the psp speakers.
Even better than my laptop speakers, I plug them into my laptop to watch all my anime now.
I'm loving Logitech's accessories between the playgear amp and playgear street, I don't know what's left to get!