Recently I was researching a topic of building strong and healthy teams. To me this notion consists of two main factors:

• Team performs. That is you can rely on it to get best possible result.
• People on the team are happy. That means that feeling yourself part of the team is better than the opposite.

Characteristics of a Good Team elaborate on that to give more detailed view on what comprises a good team.

Here are also some links to resources with descriptions of different team building activities and games:

• Team Building Activities, Initiative Games, & Problem Solving Exercises
• Team Building Resources
• Team Building Games
• More Team Building Activities, Initiative Games, & Problem Solving Exercises

While I believe that team has to be in certain mental state to benefit from explicit team building activity and your day-to-day attitude towards the team and fostering right values means more, abovementioned team activities may prove useful one day.