Exercise equipment is great to have in the house. Working out at home can be a convenient way to stay in shape without the expense and hassle of a gym membership. But if you're consolidating, moving or just don't need it anymore, this kind of equipment can be a bulky waste of space in your home.
Fortunately, if it's in reasonably good shape, a piece of used gym equipment can fetch a nice price.
Sell In Person
Many exercise equipment stores will buy back used equipment. Not all national chains will do so; one of the few exceptions is Play It Again Sports, which makes a habit of buying back treadmills, weights and other such equipment. Also, local stores in your area may be in the business of buying used gym equipment. Go to whatever places you can think of and inquire if they'll buy used stuff. If not, they might be able to point you to someone who does.
You might also consider taking out a classified ad in your local newspaper offering your equipment for sale.
The other alternative is to sell your equipment online. It'll be much easier to reach a wide audience with your posting, although there may be an added hassle involved with shipping.
Craigslist is one of the most popular sites for informally buying and selling products locally. Try posting an ad on Craigslist offering your equipment for sale, and seeing if you get any bites. Shop around for similar equipment already posted to get a sense of what a reasonable price might be. You can also tell folks that they need to pick up the equipment themselves, or offer to take it to them.
You can make a similar posting on eBay, the online auction house, if you're willing to deal with shipping your equipment. Again, shop around to get an idea of the prices; eBay has the option of setting a "reserve price" on the auction for your equipment: if the bidding doesn't reach that price, you're not obligated to sell. This is a nice safety net to make sure you don't sell your stuff for pennies.
No matter where you post online, be sure to be very descriptive and straightforward. Also, pictures are very helpful for customers to get a sense of what kind of condition your equipment is in. Photograph it carefully and in good (and flattering!) light.