Debian is a Linux release, that is preffered for desktop machines, but it's been gaining in popularity as a server Operating System during the last couple of years as well. It's really stable and secure, due to the fact that fixes are released in a few days after a problem is discovered. Debian has a large support community, so if you have any questions or troubles with the OS or with any of the 30,000+ packages it is equipped with, you'll be able to contact the developers straight away via electronic mail using special mailing lists and receive a reply in just 15-20 min. The Debian community gives you the top level of support possible, as your questions will be handled by the same people who made Debian in the first place, so they have a thorough knowledge of how their own system operates. Since the Operating System is free to use and distribute, no license costs will be included with your hosting fees and you will be able to customize the code files and any other software that you install with no restrictions, in order to optimize the software environment for your sites. What's more, Debian performs really well on any kind of hardware, as it is light and quick and does not require much memory.