I don’t know how I missed out on this before, but… here it is:

Dr. Horrible’s Sing-Along Blog

It comes from Joss Whedon (Buffy the Vampire Slayer, Firefly, Astonishing X-Men) and features Neil Patrick Harris (Doogie Howser, M.D., How I Met Your Mother) and Nathan Fillion (Firefly, Serenity).

Enjoy!