Can you play PSP games on a PS3 (without hacks)?
Solution 1:
1) Not to my knowledge as it currently stands unless the game ALSO states its playable on the PS3
2) I assume you want to hook the PSP up to the PS3 to play the PSP game on the PS3 with the PS3 controller, This is also a No (You can remote in to a PS3 and play games on the PS3 that stream to your PSP... But I so far only have done this with games I have purchased digitally like Wild Arms 3)
3) The Slim PSPs (rev 2000, 3000) have a cable you can buy that allows you to play the games on a TV (Go search Amazon.com and Id suggest the Sony cables).
Solution 2:
What James said above is correct. It is also important to note that if you decide to purchase any "mini's" from the Playstation Network Store, those can be played both on PS3 and PSP despite being made for the PSP.
Solution 3:
Just to add some more information in addition to the other answers...
The PSP Go can also connect to a TV. Plus it supports control via a Dualshock 3 controller, although I believe you have to use a PS3 to set up the connection.
The only PSP games playable on both PSP and PS3 are the downloadable PS1 classics and the Minis. I am not sure if it is possible to copy the saved games between the two platforms though. Regular PSP titles cannot be played on PS3.