IHMC - Institute for Human and Machine Cognition

Creators of the CMAP (Concept Map) tool.  Some excellent resources available here for knowledge representation and sharing.

AOK - Association of Knowledge Work

Jerry Ash's once content-rich site.  Not sure how up-to-date it is, but at least it's still there!

IKT - Institute of Knowledge Transfer

UK organization that helps facilitate the transfer of knowledge from university research programs into the business world.  This organization is similar to one I'm working with in the Pacific Northwest.  Interesting to note these types of organizations are laying claim to the Knowledge Transfer title. Here's how the IKT describes it. "A new profession, knowledge transfer, has emerged to manage the process of turning technology, know-how, expertise and skills into innovative, commercial products and services."

APQC - Knowledge Management

Knowledge Management practice within the American Productivity Council has some good information, but requires membership in order to access. Some free info, but limited value.

KMCI.ORG

Training and certification in KM. On the one hand technology focused (lots of discussion of portals, open enterprise architecture) but on the other very esoteric topics like The Theoretical Foundation of Knowledge Management.  The organization has published some interesting titles by founder Joeseph Firestone and Mark McElroy.  Mark is a colleague who has done some good work on Complexity, Learning, KM and Innovation interrelationships.

Knowledge Management Professionals Organization

Focused on certification and more old school knowledge management than implicit/tacit knowledge elicit and capture, but community members often offer worthwhile info and discussion.

K-CAP

Artifical Intelligence/Expert System focused group with annual conferences.