Mikrotik is a company that designed a specialized router OS, mostly used on their hardware, but they have an x86 version also.
ROS is really stable and quite easy to configure the basic functionality.
One of the most important features is the wireless connectivity. It’s used by the Internet Service Providers to connect remote customers. It can be used in a variety of scenarios due to it’s versatility: access point, router, firewall, bandwidth manager, VPN and PPPoE server, hotspot, user manager (for VPN, PPPoE and hotspot) and much more.
You can get the demo version here and it works for 24 hours in demo mode.
More details on their website