You've got about fifteen hours to catch the three episodes (about thirteen minutes in length each) of Neil Patrick Harris's horribility on Dr. Horrible's Sing-a-Long Blog.
It's all part of Joss Whedon's master plan to throw the series out for a week and rock Show Friendlieness in the process. The epic will be available on DVD after that and for download via iTunes for now.
If you're quick, however, you can watch all three episodes for free.
Sing on with all the evilness of Dr. Horrible.