Squid (>=v2.6): transparent proxy

/etc/squid/squid.conf:

first directive becomes:    http_port 3128 transparent

iptables rule added:

        iptables -t nat -A PREROUTING -i eth0 [ -d \! 10.0.0.1 ] -p tcp --dport 80 -j REDIRECT --to-port 3128