I’ve tried various ad blockers in the distant past, but Adblock Plus (an extension for Firefox) seems to really work. And you can have it exclude certain web sites–like your clients’–where you want to see the ads. It even blocks Google AdSense.
It’s weird (and nice) to go to a site like weather.com and have nothing flashing at you. And very ad-intensive sites like boingboing.net and thesuperficial.com load instantly instead of taking five seconds to render–like most sites, the former is made better in every way by the removal of dynamic ads; the latter’s formatting is less pretty, but not quite broken.