Daystrom Institute Technical Library is great site that has info on ships, weapons, personnel, battles, etc from the Star trek universe and written in-universe.
Ex Astris Scientia has information on just about everything from the Star
Trek universe. A lot of analysis of trek stuff from a
real world point of view. Some fantastic in-depth articles on starships
can be found here .
Star Trek Expanded
Universe is a wiki for fanon projects. That includes fan fiction, films and RPGs.
Star Trek: Phoenix-X is a script-based fan fiction
series that follows the crew of the USS Phoenix-X. It is more of a humorous series and if you like to laugh it is a good place to go. It also has
a comic series that goes along side with the writing.
Trek Writer's Guild is a site that hosts and links to Star Trek fan fiction (including linking to Swiftfire stories).