As a developer myself in the area of online tools (like domain/website estimators) i found this one of the better articles on it with 15 links to sites:
[url]http://mcjonline.com/blog/websites-to-calculate-your-website-worth/[/url]
Ofcourse a test like this doesnt give a "real-world" value of your domain, but it does give a lot of information that will be usefull while considering buying/seller domains/websites
The factors used in the calculations are a combination of serveral statistics which are optimizable
Great article with links on domain/website value