The reason that mods are pc and xbox only is that there is no encryption on either. On ps3, you would first have to break and repair the encryption. To do so, you would need an FTP server(to transfer the files from your PC to your ps3), some sort of mod that is written in ps3-speak, and a way to install the mod. The only way to use an FTP server and to remove the encryption was with a jailbroken ps3. Since sony patched jailbreaks with their 3.56 OFW, you can no longer do any Fallout mods. I'm an amateur hacker, but im confident that you cannot mod FO without a jailbreak.
PS, If you want a website to find mods, i left links at the bottom
Fallout 3-
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Fallout New Vegas-
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