Google's Personal Blocklist Chrome extension is a great way to keep unwanted sites out of your search results. A new tweak now allows you to export that list of blocked sites directly into your Google Account, which will then block those sites whenever you're searching and signed in.
Why would you do that? The biggest advantage is that your list of blocked sites will work on any computer you sign in on, even if you're not using Chrome. It also obviates the need for the extension in Chrome itself, since the blocking will be handled via your account. Hit the link for full install details.
Export your sites blocklist from Chrome to your Google Account [Inside Search]