That keeps a second list for adblock updated anytime you want. I use it, it is awesome.
[link|https://addons.mozilla.org/extensions/moreinfo.php?id=1136|Adblock.Filterset.G updater].
It freakin ROCKS.
It also can do javascript blocking as well. Pretty much any "defineable seperate URL object" can be blocked.
There are GREAT extensions for the cookies and javascript as well. Squid supports you putting any headers you want removed and added. Those being replacements as well.
I used to used something like "Infernal Nutscraper build 69" as the User Agent replacement for everyone at home.
I'd put squid ahead of privoxy if you are doing it right. Otherwise squid will miss much stuff that is should cache.