You should use Ebay to set up a 1,3,5,7, or 10 day auction. Sitepoint has a famous forum with a sell Your Site category.
A new site that is starting up is www.onlineflipper.com they sell ebooks, let you list your online services like traffic and such as well as let you buy and sell websites.
I've heard of some marketers buying sites off EBay and then selling them on Flippa. You can get cheap sites on EBay, but....you get what you pay for.
About 7 years ago I bought one off ebay for $0.99. At the time I didn't know what I was doing, but the person that created the site actually did a good job as far as set up and graphics. I just didn't know how to promote it way back them.
Flippa is really good, other than that for high value sites SEDO and Afternic are also very good for forums - DP, Warrion and DNForum is gud
Flippa is great for selling websites, but I thing there's better deals here if you're looking to buy.
I only use flippa. But I might consider the other ones you posted right there. i dont think you will need for more sites to market on if you already trust the one you are with.
I also know some goods sites for selling websites such as: Flippa.com buysellwebsite.com Dealasite.com these are the sites for selling websites but i advice you Flippa.com is the best for selling your websites..