  This survey presents some recent results by the authors and Polterovich on
the topological properties of ruled symplectic manifolds. The bundle M \to P
\to B that is associated with a ruled manifold has the group of Hamiltonian
symplectomorphisms of M as structure group if the base is simply connected.
Thus information about Hamiltonian bundles gives stability results for ruled
structures as well as obstructions to their existence.
