Sure, just drag me into this ;)

Sorry to say that any free off the shelf software I have seen do this
does not work well with content.

The whitelist idea is the safest and most effective, even if it cuts off
good pages it is easy to update on request.

I use the API in my proxy and feed the data stream
thru a Perl script to rewrite WWW pages and add my banners.
Because everyone on the web writes crappy non-standard HTML
I have trouble with my own scripts being able to identify
HTML content as it streams thru.

I think that any proxy should have something similar as a feature
since it is just STDIN STDOUT being handled.
Its really nothing more than regexp handling so be prepared for some
hairy script generation.

Oh yeah, unless you are examining content, then proxies like mine
can be configured to bypass any filtering scheme you create based on URLs.

I will be doing URL obfuscation/hashing by next year which 
will be designed to defeat any filter based on URL.

It seems like on Mon, Jul 31, 2000 at 06:14:09PM -0700, plug@arcticmail.com scribbled:
Orig Msg> 
Orig Msg> ObJLF:  You know, you could combine my
Orig Msg>         anonymous web proxy with the
Orig Msg>         jarjargonizer to bypass a web
Orig Msg>         content filter...
Orig Msg> 

JLF Sends...
-- 
When I said to people to use PGP/GPG for all email they laughed at me
and said they don't use encryption because they have nothing to hide
or it was too hard to learn and use.
When the press released that the USA FBI Carnivore system and UK RIP bill
allowed for easily reading their email, they called me to ask for help 
configuring PGP and GPG. I laughed.                ( J.L.Francois )