If I had any talent whatsoever in the area of graphic design xScope would be a go to app in my toolbox. xScope, for those not in the know, is a great little app that makes measuring onscreen elements a snap. xScope 2.0 raises the ante by adding a Dimensions tool that works as if by magic. Turning on the Dimensions tool lets you find dimensions between various elements (or using a lasso tool) quickly and easily. It is tough to describe, but check out this cool video of it in action.
There are a bunch of new features and improvements, all of which are listed here, which make xScope 2 more than worth the $26.95 for you pixel pushers out there.