There's also JPL's ephemeris service, Horizons. Horizons doesn't do plotting, but one nice thing that it does is to search for times when specified criteria are met -- e.g. you can require that Io be just leaving eclipse, at night, and at least 15 degrees above the horizon.
Bureau des Longitudes, France: Their site includes planetary and satellite ephemerides, and an interactive site giving 1997 mutual event geometries.
DOS C programs for predicting Galilean satellite phenomena, written by Eran Ofek.