
Aiera was made by Withstand the Fury Dragon to continue the legacy of Ultima: The Reconstruction when it became silent and out of date. Aiera was for a long time the top Ultima remakes hub, hosting downloads of the Ultima remakes, and posting news regularly about them, until it was reincarnated as The Ultima Codex by the same author.
I had assisted in the creation and maintenance of Aiera, and Withstand the Fury Dragon and I have often collaborated to bring the best of Ultima news and resources to the Ultima community.
Ultima: The Reconstruction was the first site that took care of listing all remakes and archiving their releases in case they eventually died down.
Arcana Dragon's Ultima Archive consisted mostly of downloads, though there were also some text files and screenshots.
Iolo's Lute specialises mostly on Ultima 7 (parts 1 and 2) but also has a section dedicated to Ultimas 1-6. The information for Ultimas 1-6 seems to be taken from other sources (especially the Ultima Web Archive) but the Ultima 7 parts are really detailed and apparently original. Even sidequests are well explained.
The World of Ultima was one of the oldest Ultima sites, established in 1995. It had several Ultima pictures and music files, along with other files you can download, including a program that can take screenshots of Ultima games.
Ultima Lives once had an archive of resources taken from other sources.
Auric's Ultima Moongates was a great resource site, containing a mix of 'borrowed' resources and resources made by the webmaster himself. While the actual site is already extraordinary, the Ultima 4 Annex it hosts is probably the best Ultima 4 resource on the net, containing even a dynamic map and descriptions of important objects, among other things.