Nesterj is the one and only, best NES (Nintendo Entertainment System) Emulator for the PSP. This Version has no bugs and works on Custom Firmwares ranging from 3.XX – 6.XX Kernel Custom Firmwares. I have personally Placed a couple of Roms within the ROMS folder inside the Nesterj folder, so the Emulator is ready to go as soon as you install, to add more roms, read the rest of the description. 
To Download Nesterj:
http://www.megaupload.com/?d=8EBRENQ8
To add new roms just download them, extract them (if they are .zip or .rar files) and place them within the Roms folder within the Nesterj folder.
To Download ROMS/Games:
http://doperoms.com/roms/Nintendo_Nes.html
Duration : 0:6:34
http://www.PspGoDownloadCenter.com/
I was given a psp slim with a broken screen. I replaced the screen then went about seeing how I could get homebrew onto it. I came across the ChickHEN R2 tiff exploit which permits one to run homebrew with out purchasing any additional hardware or changing the firmware. Implementing is very easy and after which you can run the multitude homebrew apps available for the psp. In this video I run through a number homebrew emulators for the PSP.