Scope: creating a firewall/(mail)gateway for a small network (say 10 to 15 users or so on a PIII 450MHz, 512 MB ram and two identical network interface cards, broadband connection, fully featured, for a bussines environment.
Read it on http://www.howtoforge.com
Expected audience: (beginning) sysop.
This tuto leads towards a solid 'ready to go' sytem. The fun part, I think, (tweaking and tuning etc.) starts when you are done. You may wish to inspect your logs to find clues as to where the tuning should start. Munin might tell you a lot as well.