I have been trying to sell my Fostex FR2-LE on amazon.com and craigslist.com but Its just not getting sold. What other sites do you use to sell and buy used gear?
That's the kind of item that people need to be looking for if you want to sell it; and we're kind of a niche crowd.
Ebay's an option, you could also try the "discussion group" on http://jwsound.net (there's a "want to buy - want to sell" category). You may also want to consider a consignment sale through houses like Trew Audio or Location Sound. Another possibility is that perhaps a rental house would consider buying it from you; probably not all that likely, but you never know. In any case, I'd say you shouldn't expect a quick turn-around.
I sold my FR2-LE on Ebay fairly quickly. I think I only had it up there for a week or two.
All of the ways Shaun mentioned are good options as well. Trew, Coffey, and Tai all have consignment sales that you could probably sell through.
You might try shooting an email blast out to some of the yahoo sound groups (Sound_Design, phonography, gameaudiopro). That would shoot out to people who would have a use for it.
If you post it up on ebay or somewhere else and you are a twitter user you can join the Sound Designers "Twibe" I created and post it there. It's a pretty solid network and many of the users will re-tweet it to their network to help.
All the other mentions are good outlets.