It appears that there is no free to use website for gauging the balance of public opinion - good to or bad - for a specified keyword or phrase. This keyword could be a product, brand, country, website, whatever. Now I did find that a company called SkyGrid does offer a similar service but it is not free (according to GigaOm it costs about $500 a month) and it appears to be for use with brand/company names only.

It seems to me that there is room for a similar product with wider appeal and which in true web 2.0 fashion would be free to use. It could be ad-supported of course but I would imagine that more a creative business model could be found - for instance a basic service could be offered free and a premium features offered for a fee - richer data for example or analytics.