Bwahahahaha!

Science is cool, but mad science is even cooler.

• Dr. Horrible is a 45-minute musical by Joss Whedon (of Buffy, Angel, and Firefly). It will probably get its own post later.
  
• Narbonic is a (finished) comic strip about the adventures of a mad scientist and her henchmen.
• A Miracle of Science is a (finished) graphic novel: She's a psychologist, and a member of a group mind. He's a detective, hunting down mad scientists and bringing them to justice (or at least therapy). Together, they fight crime! 435 pages of mad science, space battles, robots, and true love.
• Girl Genius is a (ongoing) graphic novel set in a steampunk Europe. The artwork is just beautiful.
• Wikihistory is a short short story about time travel, in the form of message board posts. It doesn't quite fit the theme, but what the hey.
  
• Casey and Andy is a (finished) comic strip about two mad scientist roommates who periodically die. It's not really up to the standards of the rest of this list, but it is funny.