We all go through it. Over the years we accumulate old camera lenses and bodies that gather dust on the shelves. It’s time to clean off those shelves and make a little money in the process. However, if you are like many of us you will probably plow the money back into more equipment and accessories. A great place to buy and sell equipment is MPB | Buy or Sell Used Cameras & Lenses of Brooklyn, New York. I’ve used them over the past several years and firmly believe their trade-in and sale values are fair. The process is easy to use so give them a try…and, no this is not a paid commercial. 
MPB Reviews: Buy Or Sell Used Camera & Lenses (photographytalk.com) is a good review of MPB.