You know the old saying that one man's trash is another man's treasure. At Swap.com, a marketplace for trading just about everything, you can take your unwanted "trash" (like bad Christmas presents) and turn it into "treasure".
The free service simply facilitates old-fashioned bartering: You add items you have to swap, then browse for stuff available, and work out the details with another swapper (you make an offer and can complete a swap by shipping items or meeting up locally). Because Swap.com claims to be the biggest community of swappers in the world, there's a good chance you'll find something you want. You can even trade group deals and gift cards.
Swap.com works on the honour system, but swappers are given ratings so you can decide whether or not to trade with certain people.
If you have something you can't find a good use for, check out Swap.com to see if someone else can -- and save yourself some money on stuff you actually want.