On my windows machines, I use the hosts file from "http://www.mvps.org/winhelp2002/hosts.htm" which removes a lot of junk from the internet.
Rather than going to each machine an installing this hosts file in \windows\system32\drivers\etc I would rather have my firewall block these names instead. Please note the blocking has to be done on the name, not the ip address. The ip address could easily be at some hosting site, and also be used for some entirely valid web site. Does any one know how to implement this?