Slate and fellow green blog TreeHugger have just launched an eight-week Green Challenge carbon diet. The goal: to get readers to cut their carbon emissions 20 percent through the usual variety of actions. The kicker: an interactive “my emissions” evaluation tool that friends can use to challenge one another. Nothing like a little competition to spice things up.

(I’d love to share my results, especially since this week’s theme is transportation, but it’s not yet working for me. Anyone else?)