I also recommend McAfee SiteAdvisor plugin for IE or extension for FireFox. Tells sites from Good to Bad.
It shows on links in Google Search, and when you are browsing anywhere.
Download links and Info:
IE:
http://www.siteadvisor.com/download/ie.html
FF:
http://www.siteadvisor.com/download/ff.html
Preview: (Firefox Extension)
