Jazz is an extension to the Eclipse IDE with collaborative features. 

See [http://www.acmqueue.com/modules.php?name=Content&pa=showpage&pid=104&page=5 an article in ACM Queue], or [http://domino.research.ibm.com/cambridge/research.nsf/2b4f81291401771785256976004a8d13/7ee2b2e5648ab96885256dc7006fc670?OpenDocument IBM technical report 03-12, "Jazzing up Eclipse with Collaborative Tools"].