Two Moons, one orbit
That isn't stable, and ends in disaster. If the moons are small, you can do one of those stange orbit-exchange systems, but they don't work for large moons because you end up inside the Roche limit at close approach to each other.
What is more likely is two Moons that are in distinct oprbits, perhaps with a 1:2 or 1:3 or 2:3 resonance, which would give you some interesting Calendar implications.
Go read up about some of the orbital games played by the Moons of Jupiter and Saturn, and check out Cruithne http://en.wikipedia.org/wiki/3753_Cruithne , and Janus and Epimetheus http://en.wikipedia.org/wiki/Co-orbital_moon