You can either determine the value of a website manually; Ghacks lists one such method.
You can also request a paid evaluation of your domain / site from several services if you are really keen on selling.
One method to give you a rough idea of valuing your website is to use an automated tool.
The first tool is dnScoop which is dedicated for this purpose only.
dnScoop evaluates the value of the domain by checking its Pagerank, Inbound Links, Alexa Traffic Rank, Domain age and the number of indexed pages.
The second tool is CyberWyre’s Website Value Calculator. This tool uses the sites Alexa Rank, Pagerank and Backlinks (inbound links) to calculate the value.
The former tool valued this blog at $7560, while the latter valued it at $8,007.
How much would you value this blog? How much are your sites valued at?