Vyatta is pretty good, although the firewall rules can get overly verbose quickly. Also pfSense might be good to look at.

I am currently looking for a groupware solution for our company... But everyone looks to be bumping heads. If someone in the community would just use Postfix, Cyrus or Dovecot and other open source technologies instead of writing their own, maybe there would be a decent groupware solution for linux. Egroupware is close, but their interface sucks and is overly complicated. Zimbra looks nice, but requires their own versions of everything, plus their license is not total open source. Citadel is also close, but they too have a crapy looking interface and also have a different language for a lot of stuff (Rooms etc). Does anyone know of a good groupware solution for Linux?