The developer know as zx81 has released new versions of the emulators for the PSP that emulates games from the Atari 7800 and the Atari 2600 and both are compatible with the new PSP slim.
Here is some info
Quote:
Atari 7800 emulator 
Notes for this version: - Compatible with custom firmwares 3.x and PSP-slim - Add a simple intro splash screen - Support iso8859-1 fonts in print text functions (might be useful to translate psp2600 menus in german, french ...) - Bug fix in file requester
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Quote:
Atari 2600 emulator 
Notes for this version: - Compatible with custom firmwares 3.x and PSP-slim - Add a simple intro splash screen - Support iso8859-1 fonts in print text functions (might be useful to translate psp2600 menus in german, french ...) - Bug fix in file requester
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Download
2600
http://psp3d.com/downloads/files/1190146607.zip
7800
http://psp3d.com/downloads/files/1190146688.zip
Source
PSP7800 PSP2600
I haven't tried them out myself so tell me if they work and you are on your own getting the games because it is against the site rules to post a link to stuff like that since it's illegal.
Linear Mode
