Google's AdSense announced on its blog today that it is redesigning three content ad units. For leaderboard ad units (728 x 90), the titles, descriptions and URLs are now arranged in rows, and for medium and large rectangles (300 x 250, 336 x 280), the URLs are now in the same lines as the titles. The post also said that in certain cases there will be minor adjustments to the font sizes.
You may want to see for yourself how the new layouts look, and Google is encouraging feedback from users to gauge the overall response. Judging from comments to the blog so far, it's been favorable.