LinkParser helps you analyze the links on the page you are on at that very moment. It can differentiate between 9 different types of links and can mark them in different colors. Very customizable.
Here is more about the add-on from the developers:
Linkpaser can differentiate the following type of links in order to count them or mark them on the webpage: internal links, internal dofollow links, internal nofollow links, subdomain links, subdomain dofollow links, subdomain nofollow links, external links, external dofollow links, extermal nofollow links. How Linkparser shows you the information it gathers is very much up to you. It is very customizable!
Get the LinkParser at the Firefox Add-ons website.