Edited/Modded Games for PSX or anything before?

hi im new here and i was just wondering if there was a site or something where people edited or modded old games from the playstation 1 era or before? Like, it could be nintendo/sega whatever, I don't care, I just wanted to know if there were any creative modded games out there that I could use with emulators?

for example there's that new Left4Dead that's coming out in 8bit:

http://www.1up.com/do/newsStory?cId=3177515

We can't link to sites offering roms here and just about all the sites dealing with this area of Retrogaming do offer material that's subject to copyright. However a handy keyowrd for google would be something like Rom Hacks which should get you to a great rom hack and remakes site.