matthewb:

A very clever bookmarklet by Steve Souders that examines the background images on a page and automatically generates CSS sprites (and recomputes all background positions!) based on how the images are used in the page, and grouping by size. The interface displays a running tally of the number of HTTP requests saved as well as the reduction in filesize. My only (very minor) complaint is the manual work required to fold the changes back into the source CSS files, but this is genius. (via Tim Dawson)