Here is a list of selected collaborative tools currently available to anyone free from the webs:
Numbler [via MasterMind Explorer Issue 162]
and many more from a google search.
Google SketchUp A 3D modeling tool
ajaxSketch and Gliffyare web-based drawing tools that provide an environment for diagramming, creating flow charts.
Mikon vector-based drawing and sharing enabled.
Please send me more links to make this more comprehensive.
cross posted to Asynchronous Collaborative Learning Activities