blekko lets you slash out individual sites from the search results. The exclusion just applies to you so spammers can't downvote reasonable sites. Has been popular to eliminate ehow.com from results. ehow isn't enough over the line for us to ban from the crawl entirely, but a lot of people don't ever want to see them in their results.

we're still in private beta, but happy to give invites to anyone here who wants one. just email me rich at blekko.