SoL (Server optimized Linux) is a Linux distribution completely independent from other Linux distributions. It was built from the original source packages and is optimized for heavy-duty server work. It contains all common server applications, and features XML boot and script technology that makes it easy to configure and make the server work.
Thinux is a thin-client server on a live CD. It boots a network of diskless computers to automatically start an application such as a Web browser. Each thin client machine acts as a cluster node to share its processing and memory resources with each other to take the load off the server. It is a turnkey solution that does not change nor rely on your existing systems to run. By booting from a removable CD, it does not lock-in the user so it is convenient to test. It is ideal for any organizations that require large deployment of software automatically and cost effectively.
Kerrighed is a Single System Image operating system (SSI) for clusters. It offers the view of a unique SMP machine on top of a cluster of standard PCs. The goals are high performance of applications, high availability of the cluster, efficient resource management, high customizability of the operating system, and ease of use. It is implemented as an extension to Linux operating system (a set of Linux modules and a small patch to the kernel).