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

Conditional Execution Based on Host Availability
   The Answer Guy 32: Conditional Execution Based on Host Availability.
   http://en.tldp.org/LDP/LG/issue32/tag_ping.html

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

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/

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/

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/

Software-RAID HOWTO: High Availability RAID
   High Availability RAID from Software RAID HOWTO.
   http://www.linas.org/linux/Software-RAID/Software-RAID-9.html

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