Regular services go to Frankfurt and Kassel and from both cities you have extensive connections on the German InterCity train network IC, not ICE.
By plane
By plane
Marburg has no airport so head for Frankfurt/Main, Germany's busiest airport.
By car
By car
One of the few German cities not directly connected by the Autobahn, but as you are in Germany there are good alternatives ... From Frankfurt take the Autobahn to GieÃen and than the speed BundesstraÃe 3 to Marburg.