A list of online resources on the subject of clustering, caching and related technologies...

• Jules Gosnell - Geronimo Clustering - 10,000 ft Overview
• Neal Sanche and Jules Gosnell - The push for clustering, Part 2
• IBM - Understanding quality of service for Web services
• Sun Microsystems - Quality of Service Requirements
• Neal Sanche - The Geronimo renegade: The push for clustering
• Butler W. Lampson - How to Build a Highly Available System Using Consensus.
• JMOB - Evaluation of a group communication middleware for clustered J2EE application servers.
• Jules Gosnell - WADI 0.9 Released: Open source distributed session management.
• Gunter Ollmann - Web Based Session Management.
• Carlos E. Perez - Open Source Distributed Cache Solutions Written in Java.
• Jon Purdy - Session Management for Clustered Applications.
• Jakarta - JCS and JCACHE (JSR-107).
• Bela Ban - JGroups Home.
• LAMJ/Cluster - http://www.emicnetworks.com/index.php?option=com_content&task=view&id=26&Itemid=58.
• Terracotta Home - http://www.terracottatech.com/.
• Terracotta - Object Identity, Tradition and DSO.
• Jonas Bonér - Time to Throw Out Your Distributed HashMap?.
• HTTP1.1 RFC (for Cookie management)
• JCache Spec - JSR107
• Servlet Spec 2.4 - JSR154
• Servlet Spec 2.5 - JSR154
• Rahul Tyagi - Know your clustering architectures
• Mark Mendel - HttpSession v.s. Stateful session beans
• Abraham Kang - J2EE clustering, Part 1
• Budi Kurniawan - Pseudo Sessions for JSP, Servlets and HTTP
• Vivek Viswanathan - Load Balancing Web Applications
• Tyler Jewell, Lawrence Kaye - WebLogic Server Clustering
• Steve Eaton - Maintaining session data with the WebSphere session manager
• Sing Li - High-impact Web tier clustering, Part 1
• Vivek Viswanathan - Load Balancing Web Applications
• Shyam Kumar Doddavula - Clustering with Tomcat
• Transis - Virtual & Extended Virtual Synchrony
• JCache - JCache Dev

If you are on your way through and have any references that you think would fit in here, please don't be scared to add them.