Webwork - 12:38 pm on Jun 29, 2011 (gmt 0)
There are 100s of websites where you can list a website for sale (forums, free classifieds, online marketplaces, etc.).
I think most well qualified buyers would be interested in the unique quality of the site's infrastructure (code, graphics, etc.), the unique quality of the content, and the quality and authenticity/durability of the inbound links. Pagerank, in the absence of at least 2 out of the 3 factors I mentioned, is "vaporware": the product of purchased links, homepage toolbar PR only (no internal high PR pages), etc.
The market for quality is very small, as it's pricey. The market for junk is vast and everywhere. If you have a quality site I'm fairly certain the inquiries will "come to you", especially if there is any indication on the site itself that you are looking to . . move on.