Welcome to TUG!
Unfortunately, this is a bad time to sell a timeshare. The TS resale market has really taken a beating in this economy.
If you just want to get rid of it, put it on ebay for $1.00 and pay the closing costs and you will probably get rid of it.
If you want to break even or make a profit on a unit you bought from the developer, well, it can't be done right now.
If it is one of the top resorts (Marriott, Starwood, Hyatt, Hilton, etc.) you may be able to sell it for about half the developer price, but it may take awhile - again, paying the closing costs will move it faster.
You can't post the specifics here in the forums, because it might be perceived as advertising which is only allowed in the TUG Classifieds, but if you want to send me a pm about what you are trying to sell, I'd be glad to respond. (Just click on my name in blue on the left.)