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:
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