Supply Chain Collaboration, particularly related to inventory management and collaborative planning, replenishment, and forecasting (CPFR) is a hot topic these days. On-demand applications using web services and open XML standards have the potential to make implementing a solution much simpler than in the past. Here are some links provide an overview of the concepts:

The Bull Whip Affect is a way of illustrating the increased inventory levels across the supply chain due to lack of demand information at each exchange point. This article illustrates it in more detail and has links to more information, plus you can try out the Near Beer Game which really drives the point home.

A good description of CPFR from VICS (PDF), a consortium that publishes standards for CPFR.

Another article on the VICS site discusses what the author calls the Digital Economy (PDF) or "Digiconomy". Much of it is related to supply chain collaboration.

Finally, this long paper from CAPS Research goes into a huge amount of detail on Achieving World-Class Supply Chain Collaboration. The site requires a free registration.