The first answer given requires signing up to those forums, but if you want without signing up then I know where! Go to http://campolar.net.tc and then to downloads and then select Sony PSP Games and u will get a list of many games. More games are added every day.
I guarantee most of these games work if u have an OE Custom Firmware with an “ISO” folder in it, or an ISO and CSO emulator like devhook. If you have a firmware newer than 3.40 then you can update it to 3.52M33. To download them go to: http://campolar.net.tc and then to Download and then select Sony PSP games and read the NOTE at the top and have loads of FUN!
..::Campolar®::..http://campolar.net.tc

utorrent.com
campolar and the my pspdownload info sites are scams.
they will take your money and run.
NO LEGITIMATE SITE SPAMS TO ADVERTISE.

http://emultrav20.proboards80.com
any game you want as long as you have a PSP

There is no emulated copies released on the net without question.But you can find a best PSP download site following these Checklist:http://www.download-for-psp.info
A Quick Checklist In Choosing The Right PSP Download Site
Is it a legitimate site?
Do they offer unlimited 24/7 downloads?
Do they have extensive databases of games available?
Do they have extensive databases of movies available?
Do they have extensive databases of music available?
How fast are the download speeds?
Are the games download there high quality?
Is the music download there high quality?
and more more….
You can go to visit http://www.download-for-psp.info to find out more reviews,comparisons and download links….