If there is a mail box or a community bulletin board at your home resort, you can put a “For sale” sign.  This will pressure the developer specially if they sell it for $20,000 USD and you offer it for $5,000.  Sometimes on the fine print of some sale agreements says that the developer has the first right to buy if your place is ever sold.  I have heard of developers paying the money (as long as is not too much) just to take the sign out.

 
To resale or rent  a timeshare is a hard task, the basic rule is not to pay money up-front, don’t be another victim of a scam.

Unfortunately over 50% of people that really need to sell their timeshare falls for this resale scams where they charge money upfront and less than 10% of them use their only real option which is to post it or offer it trough free advertising options as much, and as many sites as they can (it is ok to pay a few dollars to post in a great place but no more that $20 to $30).

Timeshares do not have resale value and in most situations you would take a loss in what you paid for, as they resale for less than $2000 USD.

There are some free classified ads where you can start posting:
 
http://timeshareownerscommunity.com/
http://craigslist.com
http://ebay.com
http://recycler.com/
http://usfreeads.com/  
http://www.inetgiant.com/