AlertForce
Campaign history, with hand-drawn character portraits and maps. Also includes character sheets and adventure summaries.
More Action Fun
Golden Age campaign set in 1932. Includes background, characters, and conversion notes for Champions and GURPS.
The Unofficial DC Heroes JLA Source Page
Features character descriptions from the Grant Morrison/Howard Porter era of the Justice League. Also includes a gallery and a map of the Watchtower.
Writeups.org
Searchable detailed writeups of characters from all media--comics, movies, tv shows, and other games.