if you have a computer you would like to dedicate as a router, you could also consider using Freesco (www.freesco.org
), which is a great (&free!) little piece of software. I've been running it for a few months now, boots off of a floppy on my crappy old 486 machine with only 2 ethernet cards, a floppy drive, and a keyboard. The setup was easy, and I haven't even had to think about the thing in over 3 months, no rebooting no nothing. It just sits in my closet and does its thing.
To do any admin stuff on it, such as assigning IP addresses and such (though using DHCP is strongly recommended) you can log in remotely through telnet, or through http.
But, if you want to use the computer as more than just a router, then Samba is probably your best bet.