Linux distribution such as Ubuntu and 
Fedora are always a good choice to run a computer without having to buy the expensive Microsoft Windows Operating System license. And if you want a small computer system to simply browse the web, now you can consider Linutop.
Linutop is a linux-based diskless computer. It offers a completely silent, low-power operation in an extremely small package. Just like a Mac Mini, but with lower specification and smaller size. [via Walikard]