The article Maslov $S^1$ Bundles and Maslov Data with Bohuan Lin and Holger Waalkens has been accepted for publication in the Journal of Mathematical Physics. In the article we introduce the notion of Maslov $S^1$ bundles over general symplectic manifolds, generalizing similar constructions on cotangent bundles. We analyze the properties of Maslov $S^1$ bundles and define a generalization of the Maslov index when the Maslov bundle is trivial. In the case where the Maslov bundle over the manifold $M$ is not trivial, but there is a symplectic $S^1$ action on $M$, we introduce the notion of Maslov data which serves as a non-integrable version of the Maslov index. Finally, we use Maslov bundles to prove results about homogeneous spaces and monotone symplectic manifolds, and we consider applications to integrable Hamiltonian systems.