It's a bit hard to describe in one sentence, but I'll try: it's a three episode super-villain musical comedy. Yeah, it sounds weird. And it is. But, it's also very entertaining - especially if you like campy comic-bookish stuff, or musicals. Also, unlike most super-hero type stories, this one is told from the perspective of the villain.
It's from the twisted mind of Joss Whedon - the creator of Buffy the Vampire Slayer and Firefly. He did it as a low budget experiment during the Hollywood writers strike. If you like some of his earlier work, it's definitely worth taking a look. You can view a trailer of the show by clicking the above picture, or you can go to iTunes and buy all three episodes for $3.99 (or buy just one for $1.99; but if it turns out you like it, it'll cost you more to then buy the other two).