Some good...

What are some good PSX games to put
on my PSP?

I have all the main ones:
FF 7
Legend of dragoon
Metal Gear
Dino Crisis
Crash Bandicoot trilogy.

etc.

Anything else?

Xenosaga (or whatever the PSX one was)

Castlevania SOTN

Tobma games rule, and an old game called Jersey Devil.

Spiderman 2: Enter Electro!! thats a classic.

spyro is always fun

[ace]

Are the psx games for free? Or is it like a virtual console but for the psp?

There are no free PSX games.

Yeah, spyro is pretty fun...
but i feel like there is a void...
I can't put my finger on it..

I just thought of a good one(s):
Megaman X4, and X5

yeah, but I'm too good at Megaman X games, I beat them too fast

Don't forget about Marvel vs Capcom.

About how much space to PSX games take up? I am looking to put some on my PSP, but am runnin low on space, stupid 1 GB memory card.

1 GB could probably get you 2 games.

MAYBE 3 if you're lucky.

some games are like 250 megs, and
others go up to 600

so i really depends on what games
you choose.

Yea, that means I am going to have to wait till I can buy a 4 GB memory card, because I got some emulators and stuff on there already, and I would prefer to keep them.