drbd - Drbd is a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid 1. - http://www.drbd.org
H.A. Technical Solutions - They make reliable high availability, data replication and load balancing software solutions including H.A. Clusters, H.A. EchoStream and H.A. Fulcrum. - http://www.tech-sol.com
A High-Availability Cluster for Linux - A High-Availability Cluster for Linux A Linux Journal Article by Phil Lewis. - http://www2.linuxjournal.com/cgi-bin/frames.pl/lj-issues/issue64/3247.html
MOSIX - MOSIX for Linux is a cluster-enablement technology that provides transparent process migration between nodes in a cluster. Migration is pre-emptive and transaparent to the user; processes run remotely via distributed system calls. - http://www.mosix.cs.huji.ac.il/
Linux-HA Project - Root page for High-Availability Linux Project; goal: Provide a high-availability (clustering) solution for Linux which promotes reliability, availability, and serviceability (RAS) through a community development effort. - http://linux-ha.org/
Jungo: GO-HotSwap - Add CompactPCI hot-swap capabilities to: Linux / Embedded Linux, Solaris, VxWorks, Windows9x, Windows2000, Windows NT, and Windows NT- Embedded. - http://www.jungo.com/cpci.html
Linux Virtual Server Project - A virtual server is a highly scalable and highly available server built on a cluster of real servers. The architecture of the cluster is transparent to end users, and the users see only a single virtual server. - http://www.linuxvirtualserver.org/