Blacklist Search allows you to create a list of URLs that you can block from your search results.
To add a site that you want black listed from your search go to the Blacklisted Links page.
It also lets you create your own "Preferred Searches". These are searches that will boost results from sites that you indicate as preferred.
To create a Preffered Search go to the Preferred Searches page.
If you've added sites and you don't seem to be getting the results you expected, you might want to check out the About page to learn a little more about how Blacklist Search handles URLs. Otherwise feel free to give me some Feedback.