Instant-Grid is a Knoppix-based live-CD bundled with a pre-configured grid environment based on the Globus Toolkit. One PC started from this CD becomes the Instant-Grid frontend. It also functions as a PXE boot-server, allowing other PCs in the same local network to boot the Instant-Grid environment. Together with the frontend, these PCs automatically form a working test grid. Like with the original Knoppix, the existing configuration of the participating PC is not touched (except maybe for enabling the PXE boot-option), and remains instantly available by a simple reboot.
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).
Linux4Geeks is a LFS-based small distro which works around several problems and issues mainstream Linux distributions have. It offers different versions compiled for each architecture and has all the packages required for a slim installation including a firewall and network administration tools, amongst others.
Rocks is a complete "cluster on a CD" solution for x86 and IA64 Red Hat Linux COTS clusters. Building a Rocks cluster does not require any experience in clustering, yet a cluster architect will find a flexible and programmatic way to redesign the entire software stack just below the surface (appropriately hidden from the majority of users). Although Rocks includes the tools expected from any clustering software stack (PBS, Maui, GM support, Ganglia, etc), it is unique in its simplicity of installation.
OpenVPS is a set of software built on top of the Linux VServer aimed specifically at Web Hosting. It is not another set of kernel patches, but a set of scripts to create virtual servers, collect resource utilization information, and provide an interface to the customer as well as the administrator.