As Mike has pointed out, there has been a heaping ton of stuff added to the PlayStation Network today. Sony is doing a really good (evil) job of making me want to buy a PSP Go </sarcasm>.
Call me old fashioned, but I have my launch day PSP 1000 here, and a 16 GB memory stick, so while the form factor of the Go has me interested, I would rather just buy games on my clunky PSP. But what of the multitude of titles is worth your money? That is what I am here to help you out with.
Alien Havoc: Top-down game where you run around abducting cows as an alien. Looks fun, not that expensive, has not made me want to purchase it, yet.
Brainpipe: My first purchase today, IGF winner, fun little game. Think Tempest but you don't shoot, oh and very trippy. You just steer this reticule through a tunnel missing enemies and collecting orbs. A fiver well spent. (Screenshot is from the PC version of the game)
Fieldrunners: If you have an iPod Touch or an iPhone you may well have this at the remarkable price of $4 off. Yes, this game cost $7 on the PS Store and $3 on the App Store. Good game, have it on my iPod. Tower defense goodness for those who only have a PSP, it keeps you busy. But then the PSP also has Monsters now.
Funky Punch: Another iPhone game, which isn't really anything special, but its a fighting game - also a buck cheaper on iPhone.
Hero of Sparta: This is a great iPhone game, again it costs less on the App Store. Here you will pay $7 for it. From what I have seen this is not the better version of the game. Still, its fun, but is on sale for $2 right now for the iPhone.
Sudoku: This looks to be the same version EA pushed on the iPod and iPhone, I have it on my iPod Video, and I am not buying it again.