I find attempts to quantify online popularity in “brick and mortar“-money always quite interesting. Probably the best attempt I’ve seen so far is the service Peekstats which claims to estimate the vale of a website based on a wide range of publicly available statistics (Alexa Rank, Page Rank, Yahoo Backlinks, etc.).
What I found interesting however was, besides the “value of the website” are the estimations on the expected advertising revenues which states that Eric Goldman earns a $ 1,209 a month while Links and Law only is expected to generate $ 253 a month while the IPKats earns only $ 27 a month.
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Bottomline: Judged by how much energy I’ve invested into my blog I find Peekstaat’s judgement on my blog indeed a bit harsh 
You can check out http://www.worthysite.com also to check your website value
That’s write on it seems to be the going rate!
http://www.sitefile.org/ericgoldman.org.htm
That one says $6,840 – $14,169
Thanks for the valuable info on peekstats, when valuating a website you should also consider http://www.websitevaluebot.com as it will give you a value based on every aspect of the fundamentals of a website except for revenue which is the only real way to work out a websites value.
For true value of a website you should calculate monthly revenue times 6-12 depending on brand name, age and content and this is the reason no website estimator online is accurate.
Here it is a website evaluation algorithm I developed myself:
http://www.webuka.com/
I have used Google PR, Alexa Ranking, Alexa back-links and Compete Ranking as input parameters.
Enter your URL and you will have a financial evaluation in a few seconds. (your website market price and your potential monthly advertising income).