Timeshare contracts are routinely sold through all sorts of non-broker channels. EBay listings are common, though not as common for DVC as for other timeshares. EBay is actually quite a good place to buy many timeshares. Other places are TUG, Redweek, and other timeshare-specific websites.
I would think Craigslist would be a longshot, just because of the way they localize ads -- but I've seen other timeshares offered there.
As a buyer, though, purchasing without a broker offers little to you. It may save the seller 10% commission, but you're still going to have to pay enough to clear ROFR, so there is really no benefit to you.