My, that title sounded boring, didn't it? Actually I wanted to mention the American Association of Editorial Cartoonist's Cartoons for the Classroom site. Every week or so, they pick an editorial cartoon, write some explanatory text about it and put up a downloadable version that teachers can use. I like this a lot - in fact, we used one in the museum I work in last year. They've got 127 that you can download as of today, by a wide variety of cartoonists.