As far as what's up there right now, I'd say my favorites of what I've played:
WTF: work time fun - $9.99 - love it or hate it game (think WarioWare if it was set-up to feel like a job)
Beats - $4.99 - Cheap, decent music game that can utilize music you have on your PSP
Field Commander - $14.99 - An Advanced Wars clone, but with a western art style and online play/map sharing
Hots Shots Golf: Open Tee - $15.99 - Lacks the online play of its sequel, but is still a great portable golf game.
If money's no object:
Killzone Liberation - $15.99 - A fun top-down shooter that works well on teh PSP.
Ratchet & Clank: Size Matters - $15.99 - If you like Ratchet & Clank on PS2 or PS3, you'll like this.
Scorch posted in the other thread of games that are available via retail voucher, which will be on the store tonight: http://www.cheapassgamer.com/forums/...&postcount=729
I just got an email in the past hour about updating the store at midnight to coincide with the Go launch, so I guess we're doing this now. Also, there's an update current PSP owners should download now if you want to check the new content out.