My colleague Ken shared the manifesto we came up with for our (still shadowy) project:

Building consumer software is a joyous and daunting challenge. We, software developers, owe Oxygen and Oxygen’s customers every chance at success. We believe success springs from the following principles…

Give it a read. I like this one because the tone is not just inspiring, it is also rough and uncompromising with the team (manifestee?).

Manifestos are fun, free, useful in carving out a domain and purpose in your organization, and a great guide post in case you get off track.