SiteAdvisor is a new web service that makes an attempt to alleviate problems. Currently only available in a Beta release, SiteAdvisor has both Internet Explorer and Firefox versions available. In Internet Explorer it shows up as a toolbar button, and in Firefox it shows up in the status bar. The SiteAdvisor "button" shows green for trusted sites, or red for sites that are deemed "risky", "spammy", or have "excessive pop-ups". Mousing over the icon will give more detail about the ranking of the site you are visiting. You can also see results immediately in Google searches immediately following the link to the search result.

This appears to be a wonderful free service who's time has come. In their FAQ they mention that they plan to offer premium services, but that there will always be a cost-free way to benefit from their site scoring.