I got this from Jerry Pournelle's Chaos Manner website. I'm sorry, I can't find the link to the original article. (If Chaos Manner has an RSS feed, or an index, I haven't found it yet.)
It's an Internet Weather Bug, which tells you how the Internet is behaving at the moment. Apparently when there is some virus out in the wild it will change colors. I'm going to try posting this on the sidebar to the right, we'll see how it works.
OK, it looks better at the top, so that's where it will stay for now.