At work I just set up a Dell R300 server with Fedora 13, Squid 3.1.4, squidGuard 1.4, and the list from URLBlacklist. This is to run as an interception proxy (default gateway for the client PCs) and net-nanny a small user base of around 150, and replaces an aging rig running CENTOS/Squid 2.6/Websense 5. I had to put a fair amount of hand-crafting into the whole thing to get it running (like twiddling iptables for the port forwarding and NAT, ugh!), but sure runs nicely now in my "beta test". Other than the hardware, the only expense should be US $70 for each year's worth of monthly blacklist updates.
Just wondered if anyone had any tips or caveats about Squid...?