You know those links that help you share your web site with someone easily through Twitter, Facebook and other social media sites? AddThis (http://www.addthis.com) is a tool that mak es it very easy to post that link on your site or hosted blog. (By hosted blog, I mean one that is not hosted at WordPress.com).
I won’t get into the setup because it depends on where you want to add it (a web site, Blogger, WordPress…) and they give excellent instructions. I tried it on WordPress and Blogger without any hassles.