Here's a link to about a dozen charities that MAY accept timeshares. If the timeshare is worth something, they will take it for free. If not, they will charge a fee to take it off your hands (up to $1,000) Remember the yearly taxes and maintainence can run much more than that, so you are basically paying this years fees and then getting rid of it.
This link is from the Timeshare Users Group. You can also join TUG for $15 and advertise free for a year on their website.....lots of people interested in picking up an extra week.
Good luck.
Charities That Accept Timeshare Donations | Timeshare Trap
edit post....found out you don't have to join TUG to place a FREE ad on their website. Just go to the Bargain Deals section and post the ad.