Tech Crunch mentions on their site that Encyclopedia Britannica now allows Bloggers who publish with some regularity, access to their online version, Britannica Webshare, for free. All you have to do is tell them your url and a description of your site. It is their decision to accept or deny you access.
If you do get accepted, you may access directly to any full article version, and people visiting may read the full article. The visitor does not have access to other articles, though.