http://www.packetfence.org/home.html

PacketFence is a Free and Open Source network access control (NAC) system. PacketFence is actively maintained and has been deployed in numerous large-scale institutions over the past years. It can be used to effectively secure networks – from small to very large heterogeneous networks. PacketFence has been deployed in production environments where thousands of users are involved. Among the different markets are :

• banks
• colleges and universities
• engineering companies
• manufacturing businesses
• school boards

… and many more!

Released under the GPL, PacketFence offers an impressive amount of features.