Move marker along a polyline - Google Maps API V2. Remove overlay and Add overlay repeatedly to get animation effect. - Google Maps API V2. Animation of polylines - Google Maps API For Flash. I may have over played this demo on the forums already, but I think you could still benefit from it... possibly.
I'm not sure what kind of animation you're looking for on the polyline, but I would imagine something like look-up directions from here to there, then show the path drawn incrementally like Indiana Jones style. What I think you'd need to do to have that kind of control is have it calculate the directions then use the array of points along the directions to draw them one at a time with some sort of delay between the drawing of each segment.
Bill Chadwick's Google Maps Demos. GRATICULES & RINGS * Updated 20 Jan 08 * There are three basic types.
A Latitude and Longitude Graticule, a UK National Grid Graticule and Range Rings. Range Ring spacing is automatic, fixed or from an array. Rings are labeled every 45 degrees. Implementing custom IOverlay classes - Google Maps API For Flash.