Wouter Van Vugt has uploaded the latest version of Package Explorer to Codeplex. It has full editing of parts, validation against the final Ecma schemas, and several other new features, all integrated into a VS-style interface with dockable panes and other nice touches.

Read about the new features on Wouter's blog, or download it from Codeplex here. This tool can save you a lot of time in Open XML development. It also makes a great tool for doing Open XML demos or training.

Thanks, Wouter!