You may have noticed that your ISP doesn't filter pornographic and "bad taste" sites very well. Some of them wait for schools to find the offensive sites and then inform them so that in a fortnight or so they can add the sites to their filter (including some of the supposedly school dedicated sites such as schoolzone). For our school (250+ machines, most "internetable") that situation is unacceptable. I use squid2 (and the url-regex function) to provide both proxy services and a first barrier against "bad sites" including foreign languages (try www.baise.net through your filter for example) and bestiality sites (which masquerade as respectable sources). I also block obvious hacking sites, several chats and some plain bad taste sites.
It might be useful if someone could collate lists of these sites so that there is a general list new gateway servers can forbid? Any volunteers? (Sorry, I can't take it on just yet.)