I actually really like the last one, with the vague globe and trees, and I think it would work for the page header and other places where you can see it clearly, but I think the two more cartoonish ones would stand up better to being shrunk down to the browser's tab bar. Of those two I like #3 better than #1.
Heh. Right, I actually specifically liked #3 of the no-mascot options because there's a subtle alteration that includes pretty much the entire globe (western hemisphere + almost all of Asia) in one graphic, which is nice. But on the other hand, we had to rotate Japan and Australia out of existence so we could get Alaska in the picture.