Just finished reading Patrick Lencioni's "The 6 Types Of Working Genius". Oh my! Certainly a must read for teams, especially for teams after team members get promoted into Leadership roles. Puts a team into a whole new perspectiive.
I recommend all of his stuff, but if you're looking to find a way to energize your stagnant team, or don't want to lose any momentum in your existing team, it's well worth checking out.