The Interaction-Design.org Encyclopedia has just published an encyclopedia entry on Information Architecture by Michael Cummings.

See: http://www.interaction-design.org/encyclopedia/information_architecture.html

What is Interaction-Design.org?

Interaction-Design.org is all about making research accessible. We deal with human-centered aspects of technology: Interaction Design, User Experience (UX), Human-Computer Interaction (HCI), Information Architecture (IA), Human Factors, Usability, and related fields.