We used DVCresale.com. and were completely satisfied! I always had a response within hours of sending them an email even on the weekends. They gave us up to date timelines with every step.
I have heard good things about the other too. I requested info from the Timeshare Store and got a quick response. It just turned out the **** has a listing with waht we were looking for when we decided to buy.
The whole process takes 2-3 months depending on how quickly the seller responds and submits their papaerwork, be sure to factor that into the equation. Good Luck. If you haven't already, all of those websites have a mailing list to get new listing emailed to you, it is very helpful so you don't have to check back all the time.