Well, Fanfiction.net automatically tracks every fandom you write for - my current list is
Buffy: The Vampire Slayer, Angel, Sandman, West Wing, Stargate: SG-1, Buffy X-overs, Harry Potter, Batman, StarTrek: Deep Space Nine, Pirates of the Caribbean, X-overs, Marvel, Men In Black, Lois and Clark, Highlander, CSI: Miami, Doctor Who, Book X-overs, Superman, Torchwood, Misc. Movies, Babylon 5, NCIS, Bones, Batman Begins/Dark Knight, CSI, Wildstorm Heroes, Misc. Comics, Misc. Books, Misc. Tv Shows, Superman, Dogma, Vertigo, Green Lantern, Lord of the Rings, Mission: Impossible, Terminator, St. Trinian's, Thunderbirds, Smallville, Janet Evanovich, X-Men, Wonderfalls, Captain Scarlet, CSI: New York, Wallace and Gromit, MI-5/Spooks, CHIPs, Veronica Mars, Constantine, Perry Mason, Watchmen, Dead Like Me, TV X-overs, Doom, Dexter, Movie X-overs, Scooby Doo, James Bond, Sarah Jane Adventures, Battlestar Galactica: 2003, Austin Powers, Terminator: Sarah Connor Chronicles, Discworld, Good Omens, Space 1999, Supergirl, Young Wizards, and True Blood.
More Buffy / Angel crossovers than anything else, with CSI and Harry Potter in the lead for number of words, probably followed by all the different L&C / Superman variants.
Twisting the Hellmouth actually tries to track the top twenty characters you write by counting the number of words of speech they're given - while their system isn't perfect, my current stats round out to:
Willow (Buffy) 63k words
Buffy 31.4k
Dawn (Buffy) 30k
Harry Potter 20.7k
Xander (Buffy) 18.1k
Superman 16.8k
Angel 16.4k
Billie (Billie Newman from Lou Grant) 14.6k
Catherine (CSI) 13.8k
Jack (Stargate) 13.5k
Lois (Lane) 12.7k
Cordelia (Angel) 12.6k
Grissom (CSI) 12.4k
Supergirl 10.3k
Tara (Buffy) 8.9k
Spike (Buffy) 8.2k
Kennedy (Buffy) 8.2k
Giles (Buffy) 6.5k
Sam (Stargate) 6.4k
Simon (Templar, The Saint) 6.1k
