Any version of *nix but you have to be a network wallah to get that going.
Check out Astaro in parallel to Smoothwall. Astaro has a lot of the same kind of features, DNS, DHCP, proxy, anti-spam, anti-virus, blah blah blah
m0n0wall is a great distro if all you want is "router" functionality. You can boot from CF or USB and it is extremely lightweight so you can easily build a no-moving-parts system.
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Companion - E8400 - P5K SE - EN8600GT SILENT - 2x1G Ballistix (POS) - WD250 - X241W
Server - Q6600 - P5E WS Pro - EAH3450 - 4X2G Redline - WD250 - Pioneer DVD-212
On the shelf - P5N32-E SLI - BFG 8800GTS 640M OC2 - Ballistix 2x1G 8500 4-4-4-12 - X-Fi Fatal1ty - 1xWD 150 Raptor |