What if you could get new stuff without slapping down your plastic? Well, a fresh crop of trading websites lets you do just that: Free memberships on swaptree.com, paperbackswap.com and titletrader.com connect you with people who want your old books, DVDs, CDs and video games (don't front, you know you have a secret stash.) In return, you can score some great additions to your entertainment center, without shelling out more than the cost of postage.