Good starting links:

• The CMU Artificial Intelligence Repository was established by Mark Kantrowitz in 1993 to collect files, programs and publications of interest to Artificial Intelligence researchers, educators, students, and practitioners.
• Multi-Agent Systems. This site contains pointers to information about multiagent systems, including both research and industrial references. The front page also has breaking news of some relevance.
• AgentLink - a network of excellence for agent-based computing.
• AgentCities - a global, collaborative effort to construct an open network of on-line systems hosting diverse agent based services.
• UMBC AgentWeb - a collection of items that offer an introduction or overview of key agent-related concepts and technologies.
• AgentSociety.

On-line bibliography links:

• The World Wide Web Virtual Library: Artificial Intelligence.
• Bibliographies on Artificial Intelligence, part of the Collection of Computer Science Bibliographies.
• The Springer LINK - Computer Science Online Library.
• CiteSeer - Scientific Literature Digital Library.
• DBLP - Computer Science Bibliography.

Online journals:

• The Journal of Artificial Intelligence Research.
• The Journal of Artificial Societies and Social Simulation.

Essential BOOKS on agents and multi-agent ystems

• M. Wooldridge. An Introduction to Multiagent Systems. John Wiley and Sons Ltd, 2002.
• M. d'Inverno, M. Luck. Understanding Agent Systems. Springer Verlag, 2001.
• M. Wooldrige. Reasoning about Rational Agents. The MIT Press, 2000
• Gerhard Weiss (Ed.). Multiagent Systems: A Modern Approach to Distributed Artificial Intelligence. MIT Press, 1999
• J. Ferber. Multi-Agent Systems, Addison-Wesley, 1999.
• M. Huhns & M. Singh (Eds.). Readings in Agents.Morgan Kaufmann, 1998.

A list of must-read ARTICLES

Standards organisations:

• FIPA - Foundation for Intelligent Physical Agents.
• Agent UML.

Agent platforms:

• JADE.
• FIPA-OS.
• ZEUS.
• A huge list of agent software can be found on AgentLink' site.

Mailing lists, search engines:

• Agent Digest

.
• DAI List

.
• Agent People Finder.