Do remember that the polarizer will prevent up to two stops of light from entering your lens. If you use this to remove the reflections from interior exhibits, I doubt if you'll be able to get a fast enough shutter speed to freeze action, let alone to handhold, unless you want to setup a tripod and don't mind shooting subjects which are less inclined to move eg. snakes, big insects.
As Solarii mentioned, move your lens closer to the glass to cut off reflections, and adjust the angle of the lens to the glass as necessary to minimise the effect of reflections in your image. However you'll need a lens with quite a close focusing distance, otherwise you might be too close to the subject to get a focus.