http://www.inform.umd.edu/MDK-12/homepers/emag/

This place has it all. Here you can find many projects for all
 grade levels. You can also join their mailing list and e-mail on a
 regular basis announcing new projects. You can also announce
 your project here and visit their archives for ideas on creating a
 project

Collaborative projects are listed under subject areas.

Linda Mckeown is the moderator of this site. Here you can find a travel buddy for your class and subscribe to their mailing list so that you can put out your own ad. There are online mentors to help you with a travel buddy project.

Nancy Walker's page offers descriptions of monthly and ongoing projects.

The author of this site is Judi Harris. Dr. Harris is a professor at the University of Texas at Austin. Dr. Harris has done extensive research on the topic of Internet collaboration. Her web site offers everything you could possibly want to know about project planning, coordination, assessment and online resources. There are also links to her presentations and published articles