The hacking community has always seemed somewhat scattered about the internet, divided into small niche groups based around specific tools (such as Pk Hack). Occasionally someone tries to create a comprehensive website that encompasses a wider range of hacking projects, with varying degrees of success. Data Crystal is a community/wiki that tries to consolidate all ROM hacking projects.
Data Crystal seeks to be a centralized repository of hacking knowledge not specific to any one game, series, or system. 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, Data Crystal will become the repository of all known hacking information.
Despite a somewhat sporadic update schedule (which is really the nature of any community driven wiki), Data Crystal proves to be a very valuable hacking resource. Popular hacking games such as EarthBound, Super Mario World and Super Metroid all have extensive listings, while entries for many other lesser-known games at least have links to useful websites and tools. If you are interested in hacking a specific game, Data Crystal is a great website to point you in the right direction.