I'm a huge fan of the Dresden Files novel series by Jim Butcher.

One thing I wasn't expecting to discover was that a huge number of the characters from the books have their own Twitter accounts:

• Harry Dresden
• Bob the Skull
• Mouse
• Michael Carpenter
• Molly Carpenter
• Ebenezar McCoy
• Toot Toot
• Carlos Ramirez
• Queen Mab
• Thomas Raith
• Will Borden
• Marci Borden
• Waldo Butters
• MacAnnally

I don't know who put this together, but this is serious cool :-)

I'll update the list as I find more.