Amazon is the site for many to buy books, dvds, etc.  You can sell your books and other products on their site for a fee.  Interested? Click here for more information about Amazon Services for sellers.

Ebay is an online auction site that is good for many items, including clothes, collectibles and housewares.  Fees are charged to the seller upon sale.

Craigslist is a site for online classified listings.  Listing is free. This site is good for items to be sold locally (i.e. too heavy to ship).

Cash4books is a site that buys used books and includes free shipping labels for you.

Gazelle.com pays cash for your unused electronic gadgets.

Local consignment shops are also a good place for clothing, shoes, and home furnishings.  Visit http://www.narts.org/ to find one near you.