Auric's Ultima Moongates is a website dedicated to all things Ultima, but specially focused on Ultima IV. It includes some MIDI files of in-game music, a short history of the Ultima games and various downloads.
The Ultima IV Upgrade Patch is available from this website. It is the home of the project, and therefore the latest version can be found there. Also complete maps of Britannia, the cities and all conversations from Ultima IV can be found there. A complete destination guide for the moongates (Flash player needed) and several hints are also included.
Several sections of the site appear to unavailable or broken, and the site is no longer updated, but it is still online as of October 2010.