Squid supports transparent caching, allowing all web/FTP access from your desktop machines to use the cache without having to configure the web browser on each machine.
This is easily done by simply redirecting all outgoing web and access to the Squid machine on the desktop machine's gateway. If that's a Fedora machine, then do the following:
Enable packet forwarding.
Graphically: Main Menu => System Tools => More System Tools => Kernel Tuning. Type in the root password if asked. Then click IP, IP [2], then IP Forwarding. Then click Save, then Activate Changes.
Command Line: Open up /etc/sysctl.conf with a text editor (for example, nano) and make sure it includes the following line (its likely the system currently has the line but the number is set to zero - change it to one):
net.ipv4.ip_forward = 1
Then run
sysctl -w
to make the changes take effect immediately.
Add a rule to your firewall to intercept HTTP connections and send them to Squid:
service iptables start iptables -t nat -A PREROUTING -i eth1 -tcp --dport http -j DNAT --to squidserver.example.com:3128 iptables -t nat -A PREROUTING -i eth1 -tcp --dport https -j DNAT --to squidserver.example.com:3128 service iptables save