Haiku

Haiku is an open source operating system under constant development. Specifically targeting personal computing, Haiku is a fast, efficient, simple to use, easy to learn, and yet very powerful system for computer users of all levels. Additionally, Haiku offers something over other open source platforms which is quite unique: The project consists of a single team writing everything from the kernel, drivers, userland services, tool kit, and graphics stack to the included desktop applications...