This would be a great list to compile. Perhaps if you've done the leg work you could share your findings with the community?
Unfortunately, with sandbox titles like this game there's lots of people independently releasing content on their own. BGG has rules for hosting copyrighted content that, if followed to the letter, would prevent people from posting here, because frequently people use art belonging to Hasbro / Wizards of the Coast that they don't have permission to re-use on their game mods. That's why you see a lot of personal websites, file sharing sites, etc. Of course, keep an index could be problematic if Hasbro ever decides to crack down on the mods....
Michael Westen would find a way, lol. Loved that show.