firewall? To be used as stand alone firewall. Kind of low cost substitute of Cisco PIX or Checkpoint firewall.

Shorewall and Mandriva Linux 2006 has a nice easy to use implementation of it as well .

www.shorewall.net

This is a hard question with the information that you have provided. Is this a stand alone firewall, like a NAT, firewall, DHCP server or a software firewall for a linux computer. Hardware stand alone firewall:I have used IP http://ipcop.org/ and this is an excelent free product. I have used in the past surewall and others.Desktop enviorment firewall:Linux should have a built in firewall or one that you can get for what ever distro that you are using.

Smoothwallhttp://www.smoothwall.org