Need a good Web Proxy software/appliance

[Tsaico]

Pretty basic, it will need to work with AD though, then of course filter the internet based off of the group I put them in. Example, would be "Strict" as they only get explicitly what sites I list, "moderate" which would be the group that get internet, but NSFW sites and a few customs URLs, and then the directors just get the net behind firewall, but if they want to surf on gambling sites or pron, they can. Any suggestions? I found one from BlueCop that seems promising, but am looking for more ideas.