Friday Distro: Zentyal for easy network infrastructure

Zentyal can be configured to serve as anything from an IDS and firewall which does network routing with QoS, VLAN tagging, and VPN/IPSec, to a certificate authority, or an Exchange replacement with calendar, contacts, ActiveSync, MAPI, and Jabber for chat. It can be your VoIP server, with voicemail and hold music, or Active Directory controller and file server (Samba) supporting Windows clients.
Zentyal can even be made into a full "captive portal" gateway, like those used by hotels and other WiFi hotspot providers for displaying terms of service and possibly requesting payment information, but which can also be invaluable for allowing misconfigured laptops internet access. The usual basic services are there, like web sites and printer sharing, of course. And clustering is an option for high availability of services, if you run more than one Zentyal server.