On most websites - including this one - the footer is the boring place where you (usually) place all the pocket lint, which didn’t make it into the page anywhere else. It usually have a copyright notice, links to a site map and other stuff which may be important, but not interesting (speaking in very broad terms).
Today I came across an article on footers with great usability. Footer Usability? Yes, and from a blunt disregard and ignorance, I’ve discovered that the site footer is an excellent place to place a lot more effort.
The footer may have been important as an “end of page marker” in many designs, but using it as an active area to promote other parts of the site, seem to be a new trend from the late part of 2007.
I really like the footer usage on farfromfearless, where especially the flickr photostream adds a bit of life to the page, and ProBlogger.net, where the categories listing might act as a miniature site map.
While using the footer could be a very smart move, don’t over do it. Bad examples on footer misuse include popsugar, where footer eats up more than 30% of the total page length, and engadget, which seem to claim a lot of screen space - without any interesting content (just headlines from their sister sites).