ReturnMyPants is a free service that tracks things that you lend out to others and that you borrow from others. This is quite handy, because I'm one of those people who doesn't know where on earth my stuff are. I've found my belongings in my friends rooms years later and I also have random stuff that I don't know who to give back to.
This might be the solution to a few things. Now just to remember to make a note of the things I lend out. :-P M