The really, really good news:
There's a whole choral/orchestral rendition of the full "Spider Pig" song!
The album is comprised of Hans Zimmer's actual score to the movie, so there are no other well-known singers or bands doing fun songs. Some of the tracks are great, though, with my favorites being the high-energy "Release the Hounds" along with "Recklessly Impulsive," an electronic song consisting mostly of "D'oh!"s. Indeed, the titles might be the best part of all, from "Doomsday is Family Time" to "His Big Fat Butt Could Shield Us All," to the most hilarious "Thank You, Boob Lady."
If you want to buy the actual soundtrack on CD and can wait until July 31, you can grab one with the brilliantly kitschy limited-edition donut packaging (see above, right). Woo hoo!