Check out this Google Chrome extension:
Tired of the same spammy scraper sites and useless "Pay to view" pages clogging up your search results? Search Filter is the answer.
When installed, a delete button will show up next to the URL in your search results. When a domain has been deleted, it is removed from all search results for all search terms. An Options page is provided to remove filters.
Supported search engines are: Google, Bing, and Yahoo.
http://webapps.stackexchange.com/questions/1397/is-there-a-way-to-remove-sites-permanently-from-my-personal-google-search-resulIs there a way to remove sites permanently from (my personal) Google search results?