Check out his Dr. Horrible’s Sing Along Blog shorts. Aaaaawesome! (Neil Patrick Harris, Nate Fillion, and Felicia Day are the actors).
Update: You know what I forgot to mention? It was for a limited time only:
ACT ONE (Wheee!) will go up Tuesday July 15th.
ACT TWO (OMG!) will go up Thursday July 17th.
ACT THREE (Denouement!) will go up Saturday July 19th.
All acts will stay up until midnight Sunday July 20th. Then they will vanish into the night, like a phantom (but not THE Phantom – that’s still playing. Like, everywhere.)
Dr. Horrible does, of course, have a Master Plan spelling this out along with his motivations in great detail. It would have been advisable to read it. Oops.
Update 2: The vids are available again for a bit