Besides collecting (I mean..um...buying and using?) yarn, I also collect...
Old Navy flip flops. I never even wore flip flops until this year. Suddenly, they're the most comfortable thing in the world, and every time I go into Old Navy, I have to grab a couple of pairs (they're 2 for $5, so how can I say no?!) I am now obsessed with matching my flip flops to my outfit. Most of my clothes are from Old Navy, so it's easy to coordinate. But that's 20 pairs. Perhaps slightly over the edge. Please let's not calculate how much that set me back in the course of things.
Mr. Fiberflash really can't say anything though, since he has a few collections of his own. These three large drawers are very carefully packed full of band t-shirts.
There are somewhere between 175 and 200 shirts total.
On top of that, he also collects CD's (around 700 so far), vinyl (doesn't matter if he already has it on CD), leather jackets, hats (derby hats, top hats, newsies, spitfires, etc.) I think think that there are a few more collections of his, but I just can't think of them right now.
All of this to say, if I keep buying Old Navy flip-flops until I have every color (actually that would only be about 5 more pairs), or buy yarn until I am firmly in SABLE (Stash Acumulation Beyond Life Expectancy) status, it's all fine, because I'll have company in the looney bin.
So what do you collect other than yarn?