Sitepoint's Website Marketplace is one of the more interesting forums to watch on the web. It's also a great way to predict the quick-sale value of a web property (by which I mean the price to dump it if you had to do so in a hurry, rather than waiting for the right buyer).

The standards of sale value still include PageRank via Google's toolbar, which is interesting, though unsurprising - we've yet to see another model for global popularity that was easily recognized, and going through a site's backlink structure via a linkdomain is more for those already interested. Valuation also includes the site's traffic, its AdSense (or other) revenue, the niche (some are more popular than others - i.e. poker, sports, etc) and the quality of the domain name itself.

My favorite part about Sitepoint's forum is that you can read the replies back and forth between sellers and potential buyers and come to understand the market more thoroughly. I'm considering selling one of our internal projects and I believe Sitepoint might be a good place for it.

Any other recommendations that you use to buy & sell sites?