Harvard Business Publications -- Site for all of their famous business cases. There are teaching notes on teams, team building, and team leadership.
Self-Directed Work Teams (SDWT) -- a site dedicated just to this popular concept in manufacturing. Has some case studies on Harris Corporation and Saturn and other links.
Allstate Insurance:Taking Teams from Buddies to the Bottom Line -- Case study about what an insurance company did to build high performance work teams through a nine-step chartering process. Winner of best industry paper at 1995 CSWT conference.