Rhythm Games:

Hatsune Miku: Project Diva 1 & 2nd (soon also 2.5)

This post has been edited by Foxi4, Tue, June 14th, 2011 at 20:36

Thanks a lot, I will take a look at those videos and may even take the dust off my PSP to see if it still boots up!
That Persona 3 Portable looks pretty interesting.

We (I?) will be posting a guide on hacking your PSP with the latest and greatest CFW (a lot has changed in the PSP scene the last couple of months) within a week or so, as well, so you'll definitely want to dust off that trusty ol' PSP of yours

why I think I already tried all the games listed above

any Nathan, Rainbow Six is sucks, i mean the Vegas one of course.

Should be listed Minis too

Minis:
Creature Defense (not really a minis but it's small)
Savage Moon The Hera Campaign (not declared minis until later release)
Auditorium
Boom Beats
Vibes
Crystal Defenders (not declared minis until later release)
Pix'N Love Rush
Zenonia
Pac-Man CE
Tetris (EA)
Shift Extended
Taisen Gindan Shooting <<< Really fun First Person Shooter

Racing:
Outrun 2006 : Coast 2 Coast
GTI Club : Supermini Festa

music:
K-ON! Houkago Live! (in Japanese but playable with little to none Japanese)
Taiko no Tatsujin series (same as above)
Pop'n Music series (same as above)
DJ MAX series

RPG:
Star Ocean series
White Knight Chronicles: Origins
Shin Megami Tensei: Persona
Lunar: Silver Star Harmony

Fighting:
BlazBlue series
Tekken series

Rythm

Patapon 1-3

I destroyed my square button playing this games too much  

Updated, thanks for the suggestions!

Never knew there was a Star Ocean for the PSP btw, thanks for that.

Are there actually any real point'n'click adventure games for the PSP, a la Syberia, Longest Journey (or MI/DOTT, if one wants to get all old skool)? Or at least some text heavy ones like Ace Attorney?

To me as an outsider it seems such stuff doesn't exist at all on the PSP, that's why I never gave it a closer look.

There's Myst, but it sucks. It's just a port, nothing more (well, some minor stuff, but that doesn't matter).