High Availability Vendors

Alteon (Nortel) - Hardware based solutions for high availability
Arrowpoint (Cisco) - High-end content aware switching
Extreme Networks - Another hardware (switch) based HA solution
F5 - Home of the famous BigIP load balancer
Foundry Networks - Superior high availability, load balancing, clustering switches.  Great for implementing web server load LB, firewall LB, geogrpahic LB, and transparent cache switching.
High-Availability.Com - RSF-1 Advanced Cluster High Availability Management Software
Nokia - Home of the IP110, IP330, and IP650 firewall appliances, which come stock with dynamic failover (via VRRP) capabilities.
Radware - Another high availability hardware vendor
Rainfinity - Software based high availability\clustering solutions
Stonesoft - Software based high availability\clustering solutions

Other High Availability Sites

Networking Unlimited - Great ideas for Cisco based high availability. Home of the book, "High Availability Networking with Cisco", several whitepapers, case studies, and other useful information

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