It is a scam!
BTW - I rented a week during the Superbowl last year and the market was absolutely flooded with rentals. I ended up only getting $800 for it, which is no more than usual. I had Ads all over the place for months, and rented it at the very last minute.
Some resale companies sell timeshares and some just sell ADVERTISING and have no intention of every actually selling/renting your timeshare.
Here are some warnings signs with these kinds of companies:
1) Do they say that they already have a renter/buyer for your timeshare? (or an established market like people attending conventions.)
2) Are they offering to rent/sell it for far more than the market value?
3) Do they want you to pay a large up front fee?
4) Do they want your credit card number before they send you a contract?
If you answer yes to any of these questions, then this is the usual scenario:
Once you pay the fee and receive the contract, you discover that the company has only promised to advertise your resort, not to rent/sell it, and they don't mention having a renter/buyer in the contract.
Then, you won't hear anything from them for a long time, and when you contact them, they will tell you that the renter/buyer backed out, but they will advertise your timeshare on their over-priced website.
Finally, when you try to get your money back, they will point out that you signed a contract, and it's only for advertising. When you try to challenge it with your credit card company, they will tell you the same thing.
Please see the articles at the top of the Buying, Selling, Renting page entitled "How to Sell Your Timeshare."
Good luck!