Terminal X This is by far one of the best designed, most comprehensive X-Files pages out there. They have just about everything you'd want.
Black Knight's X-Files Page Very nice page with many pictures, sounds, links, and other assorted X-Archives.
Bureau of Federal Investigation- X-Files Division Another nice X-Files site.
The X-Files FOX's official web site.
The X-Files: 1013 Version 2 This is another really nicely designed page.
The Ultimate X-Files Repository Lots of files. Lots and lots of files.
And of course, for those poor, unsatisfied Relationshippers out there...