Looking for an app to track bands/albums

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I'm a (legal) music junkie and a bit of a completionist. If I'm into a band, I usually like to get all their albums (unless they jump the shark). It's hard to stay up on new albums, or to make sure I have all the old albums.

I've recently enjoyed using "Episode Tracker" for iPhone and fictfact.com to help me track my TV and reading favorites. Looking for something like that for the iPhone, or even a website that's usable on the iPhone.

Any suggestions are welcome!