Squirm
A flexible regex based redirector for Squid.
http://squirm.foote.com.au/

Squid-cache.org: Hypermail Archive
All squid mailing list entries from current day back to May 1996.
http://www.squid-cache.org/mail-archive/squid-users/hypermail.html

Devshed.com
Article on tuning Squid on Linux for maximum performance and stability.
http://www.devshed.com/c/a/Administration/High-Performance-Web-Caching-With-Squid/

Transparent proxying with squid and pf
Instructions on how to use OpenBSD packet filter (pf) to redirect http connections to a squid cache transparently without any client configuration. [OpenBSD]
http://www.benzedrine.cx/transquid.html

Squid: The Definitive Guide
Advertising site for a book on Squid, written by Duane Wessels. Offers chapter summaries, reviews and purchase locations.
http://squidbook.org/

Ad Zapping With Squid
A redirector for squid that intercepts advertising (banners, popup windows, flash animations, etc.), page counters and some web bugs (as found).
http://adzapper.sourceforge.net/

Squid for Windows
Version of Squid written for Windows operating systems. Free download.
http://www.acmeconsulting.it/pagine/opensource/squid/SquidNT.htm

Squid: A User's Guide
Oscar Pearson's guide to installing, configuring and running a Squid implementation.
http://www.deckle.co.za/squid-users-guide/Main_Page