FreeBSD
My favorite operating system is FreeBSD. This server runs on it and I maintain several ports, i.e. software packages. Since September 2011, I am a FreeBSD ports committer under the alias cs@.
If you need a stable and fast operating system with a very liberal license and a great community, please give it a try. In case you do not want to hassle with technicalities, use PCBSD, which is FreeBSD tailored for end-users.
