I'm probably unique among fanfic authors -- I was a pro and a member of SFWA years before I discovered fanfiction.
I'm probably best known professionally for the books I've written for Steve Jackson Games, among them GURPS International Super Teams, GURPS Camelot, and two of the three GURPS adaptations of the World of Darkness: GURPS Werewolf: The Apocalypse and GURPS Mage: The Ascension. My latest book, GURPS Shapeshifters, came out in July 2003.
As for fanfiction, I'm known for the Drunkard's Walk metaseries, of which only Drunkard's Walk II has seen the light of day as of the end of 2003.
For those interested, I have a discussion board for Drunkard's Walk and my other writing at http://pub21.ezboard.com/bdrunkardswalkforums -- new participants are always welcome.