Joss Whedon's online music Dr. Horrible's Sing-Along Blog is now live and viewable for free here and downloadable (for not-free) via iTunes. Starring Neil Patrick Harris as a would-be supervillain nursing an unrequited crush on a woman at the local laundromat (Felicia Day) as he attempts to join a league of supervillainy, it's a three-act, 40-minute musical. The first act is up now, to be followed by two more installments in the next few days.

We should have mentioned this yesterday, of course, but it's not too late and it's quite a bit of fun. Especially when Nathan Fillion shows up as… Well, best not to spoil that. Oh, and Dr. Horrible has an evil friend named… Well, best not to spoil that either. The songs are good too.