I collect rock posters or concert posters or gig posters or whatever you want to call them. I have a pretty small collection of about 8 or 9, but I am a big fan of the genre. There is a tremendous amount of creativity going on in this area right now. The book Art of Modern Rock explains the movement and identifies most of the key players. I really like Aesthetic Apparatus, Jay Ryan at the Bird Machine, The Heads of State, Little Jacket, and many others. One of the things that I really like is that there isn't one industry town that you need to be in to be a player in the industry. Chicago, Austin, Seattle, LA are as likely to have artists designing posters for shows as are Salt Lake City, Minneapolis, Louisville and Madison. There really is no one place that a poster designer needs to go to and artists from all of these places can do excellent quality work. The internet with it's ability to promote and sell posters from anywhere in the world has created a level playing field. If you do good work people will find you and buy your stuff!
Two things are holding back my collection. 1) Framing posters can be expensive. 2) I can't get myself to buy a poster for a band I don't like. There are people creating great looking posters, but if I can't say that I have at one time liked the band I can't have it hanging in my house. These are good things though. They'll keep my collection from getting out of hand.