If you have something collectible or brand-specific that's easy to ship, you can list it for sale on eBay. You'll pay a transaction fee, but it's an easy way to have people bid on stuff you want to get rid of.
An alternative: You can sell almost anything through Craigslist.org, which is free.
"Kids' items and recognizable brand names sell great on Craigslist," says Frank. "I sold a Schwinn jogging stroller, Power Wheels riding toys and a Weber gas grill in less than 24 hours."
The keys to quick sales are good pictures and accurate descriptions.
Make Craigslist transactions in cash, and if the item is small, meet the person in a public place. If the buyer comes to your home, arrange to have someone there with you, and make sure your buyer knows the dimensions of the item.
"There's nothing worse than having a buyer at your door and the only thing preventing him from getting it out of your house is that he didn't bring a big enough truck," says Jill Valeri, owner of The Welcome Home: Interior Design Solutions, who sells furniture on Craigslist.
Be realistic about pricing, too. Start at half of what you paid retail.