I've used redweek to both rent a timeshare week for my won use and to rent out time. It's mostly like the DVC points rental boards here - you have to establish a trust with the other party and need to use a contract to back-up the transaction. They have some useful guidance on the website, too, for both sales and rentals. There's a small ($25 if I remember correctly) fee to join in order to view the contact information for for sale or for rent ads, and there may have been a small fee to post the for rent ad, but quite honestly I don't recall for sure. I've enjoyed the site and feel pretty good about it as a whole.
BTW - I've also used homeaway.com for rentals, and they have a real nice site, too, with the basic premise being the same - trust between the parties. That site is mostly houses & condos for rent ... take a look. Good luck.
I like to check out last minute rentals on Tugg. There is no fee associated with the website.
I have rented a few times from a tugger. And they have Williamsburg frequently.
I'm a Redweek member (membership fee of $15/year) and have rented several times from there. We even bought a Marriott timeshare from someone there. PP has already said it right. Establish trust and use a contract. We've had great luck on Redweek.
I've used it for some time both to rent out weeks I had extra (Marriott & DVC) and on occasion to rent something to use. It's a good resource but just remember you're connecting with an individual with all the cautions and risk associated.