This Day in Led Zeppelin. The title makes it sound like all you get is a Zeppelin-themed calendar but it's much more than that.
For the bargain price of $2.99 you get all the Zeppelin trivia you can handle as well as a quiz to test your knowledge. Then there's my favorite part, the Zeppelin song notes. Every song from every album is covered here. The Rain Song is one of my favorite tunes and I just learned it was inspired by George Harrison. In fact, the first two chords of the song are similar to the opening of Harrison's wildly popular Something.
I never made that connection, but was immediately able to do so within this app. That's because This Day in Led Zeppelin looks through your iTunes collection and knows what Zeppelin songs you own. If you're reading the song notes for a tune you own you'll be able to play it within the app (while you're reading the notes). The app also knows which songs you don't own, so it features a "buy" button on those notes screens taking you to the track's album in the iTunes store. Very cool.
Additional links in this app take you to sites where you can buy Zeppelin sheet music and merchandise. I wish they'd just open up within the app but unfortunately you have to visit those pages via Safari.
If you're a Zeppelin fan you need this app. And if you just want to see an example of how a great band app is constructed, spend the three bucks on this one. You won't regret it.
P.S. -- In addition to all these entertaining features, as the app's name says, it also includes notes about what happened on this day in Led Zeppelin history. For example, did you know that on this day (February 28th) in 1970 the band played a gig in Copenhagen under an assumed name because Eva Von Zeppelin, a relative of the airship designer, threatened to sue if the family name was used in Denmark? You'll need to buy the app to see how that interesting story ended for the band...