Personal connection with the work: Invite people to reveal their personal motivation for being part of the team. What's in it for them? Start talking about why each person cares.
List issues and causes that you as a team care about. Is there any way to link the work of the project with that cause?
Satisfaction: Check regularly that people find the work absorbing and dig down to discover why they don't find it rewarding. In team meetings invite people to share what they found most satisfying about some piece of work, or recent activity.
Responsibility: As people acquire more responsibility they generally expand their effectiveness. Share out responsibilities across the team and remind people that the expectation is that they will live up to them.
Ensure that each member of the team has responsibility for creating some important team result(s)
Review how often members of the team volunteer to undertake tasks that the team needs doing. If there is a low "volunteer count" address this by exploring what is deterring people from coming forward.
Reputations on the line: There has to be something at stake if people are going to fully commit. Find ways to invite both individuals and the entire team to put their reputations on the line-for example by publicly committing to some goal or level of service.
Using individual abilities: teams are notorious for ignoring hidden talents. Spend time in a team session checking out people's total skills inventory.
Try asking team members to say whether they feel fully used within the team. Invite them to score on a scale from one to ten and then discuss how they can move further along towards the maximum end.