I've got collections of various different things. First, I'm a big fan of Pearl Jam, and I've got around 400 bootlegs (audio and video) on my computer and on CD, plus of course all official albums and DVDs, numerous CD singles and a small collection of vinyl, t-shirts, stickers and tourposters. I also have a collection of Dire Straits and Mark Knopfler CDs, videos, singles and vinyl.
Besides that, I've got a pretty complete Colecovision collection, 3 Commodore Amigas with quite some expensive add-ons and a lot of boxed games. Finally there's a few hundred books and comics, CDs and vinyl, and I've got 6 electric guitars...