Because I am using a group project in one of my classes this semester, I have been looking online for ideas of how to structure the groups and how to teach students to work effectively together. I found a great document from Griffith University in Australia that contains teaching tips, a discussing of assessing teamwork, principles of effective teamwork skills, student handouts, and more.
The University of Waterloo has a nice web-page that provides information about teamwork skills and includes links to resources on assessing group work, making group contracts, giving and receiving effective feedback, group roles, and more. You can find the site at http://goo.gl/rgz9Qk.
If you want a resource for students, Merlot II has given 4 (out of 5) stars to the online tutorial Working in Teams. Read the review or look at the tutorial.