Practically none of the grid systems accommodates the most common ad widths (120, 160, 180, 300)px well (https://www.google.com/adsense/static/en_US/AdFormats.html). I use malo (http://code.google.com/p/malo/), incidentally by the same author as this post's framework.

It's simple enough to grasp in a few seconds and it allows me to use a grid that fits well enough around most ads. It's also so small that cross-browser breakage is easy to detect.