NethServer - NethServer is an operating system for Linux enthusiasts, designed for small offices and medium...
pfSense - pfSense is a free and open source firewall and router that also features unified threat management, load balancing, multi WAN, and more
Zentyal - Linux directory, domain, mail, gateway and infrastructure server for SMBs.
Univention Corporate Server - Univention Corporate Server UCS with Active Directory functions and App Center is the cost-efficient and popular successor to Microsoft's server solutions.
Ubuntu Server - Secure, fast and economically scalable, Ubuntu helps you make the most of your infrastructure. Whether you want to deploy a cloud or a web farm, Ubuntu Server supports the most popular hardware and software.
OPNsense - OPNsense® you next open source firewall. Free Download. High-end Security Made Easy™. Offers Intrusion Prevention, Captive Portal, Traffic Shaping and more.