This is a fun way to save money and have a fun night in with friends. I read about this somewhere a while back, and though I personally haven't had the chance to try it, it's definitely something I think about.
Plan a mom's night "IN" at your house or a friends. Each person brings a food dish and an item ( or two or three) that they no longer need or use. Once everyone has arrived with all their goodies, simply display everything on a table. While enjoying the food, peruse the 'goodies' and see which items you'd like to trade your stuff for.
The actual ways of conducting the trading is prety much done however you and your friends decide you want to handle it. But the main point is that everyone gets a chance to get something "new" while giving away something at the same time.
You may come across an item that you needed to buy soon, and now won't have to. Or an item that will be a perfect birthday or Christmas gift for someone else. Or maybe just a book you have been wanting to read. But hopefully everyone will leave with something fun and useful, and will have saved money that they may otherwise have had to spend.
Another twist on this idea could be a coupon party. Everyone simply cuts and saves coupons they come across, and at the get together, coupons can be swapped and traded.
Here's to saving money!