Saw a great presentation by Tim Lind at the Peterborough/Monadnock LUG this evening comparing four Open Source firewalls: Smoothwall, IPCOP, Sentry and M0N0Wall.Each comes as a bootable CD-ROM, some install to a hard drive, m0n0wall runs off the CD-ROM with settings stored on a floppy (or, optionally, a Compact Flash or USB storage). Each supports a variety of tools, including DCHP, DNS, some varieties of VPN, intrusion detection, logging, NTP, ssh, and a couple of acronyms that flew right past me. Tim uses these to set up clients with internet access, re-using an old clunker PII-350 they clients have laying around, and getting a statefull firewall with some pretty impressive tools.