Remember when you were in school and you would bowl for charity? And for every pin you knocked down you got, say, ten cents? Or run for a dollar a mile? During the Blogathon, people update their websites every 30 minutes for 24 hours straight. For this, they collect sponsorships. Pledges can be a flat donation, or a certain amount for every hour the blogger manages to stay awake.
This is the Flickr group (obviously) for the 2009 Blogathon. Post caps of your blog, banners, photos of you ingesting obscene amounts of caffeine trying to stay up... pretty much anything (even vaguely :) related to the Blogathon.