We here at datacrystal.org are all about hacking ROMs. If you're unfamiliar with the subject, Wikipedia has an excellent article on ROM hacking.
Prior to the founding of datacrystal.org, the ROM hacking community was largely decentralized. Information on any one game would be buried in nested folders on forgotten websites. Hackers toying with games lacking sufficient fanbase would have nowhere to put their findings, and as such, the ROM hacking community as a whole could not grow. Datacrystal.org is now available to all hackers as a community to share information. If you have the greatest or the smallest finding about whatever game you like to hack, add it to the site. As the community grows, datacrystal.org will become the repository of all known hacking information.
For legal reasons, we do not host roms or emulators on datacrystal.org.