I found a great book in Wikibooks discussing Constructivism & Technology. Below are a few of the case studied provided along with others I found through google.
Willodale Elementary School has created a great series of student generated podcasts that cover subjects such as Social Studies, Science, Geography, and art.
OurCity Podcast provides a view of google maps overlayed with student podcasts describing the cities that they live in. I found podcasts from the United States, Mexico, Canada, Australia, Qatar, England, and Germany.
Students from a Philadelphia elementary school created this video documenting a cross-curricular activity and posted it on-line. A description from the posting:
This was a very powerful project that incorporated historical aspects of the American Revolution, geometry, public speaking, working cooperatively, ratio and proportion and a whole menu of grade appropriate curricular objectives and state mandated standards.
ThinkQuest provides a large collection of student created websites.
The langwitches blog describes a project where student connect to other classrooms around the world using skype. Here is an interview that has been posted on youtube. Students were able to talk with classrooms from Thailand, Spain, China, Canada, South Korean, and other schools throughout the United States.