Fastvue TMG Reporter gives you great insight into what sites are being accessed. Forefront TMG administrators are often surprised to see sites in their reports that they believed were being blocked by their Forefront TMG access rules. By running reports on these sites, they often discover that it is due to an unintended consequence of another access rule that permits traffic for a different situation.
I thought it would be useful to review the various methods of site blocking to ensure that your rules are as broad or as specific as they need to be.