For recommended timeshare brokers, see the TUG Business ratings, which is a sub-forum of this forum.
Have you done any research to find out what your timeshare is going for on the resale market? Because of the economy, most timeshares are going for 0-10% of original retail. If you find out that your timeshare falls into that category, then using a broker may not be feasible, because their commission starts at about $1,000. For a TS with little or no resale value, you may just want to sell or give it away yourself, to save money. See the article at the top of this forum for more info.
WHATEVER YOU DO, DON'T PAY SOMEONE A LARGE UPFRONT FEE TO SELL YOUR TIMESHARE - THAT'S ALWAYS A SCAM!