You can take a direct train from airports at many European cities. Usually part of the airport complex, book in advance with European Rail and avoid the hassle of missing the next connection!

Paris (Charles de Gaulle) to:
Avignon: 4hrs 10mins
Bordeaux: 4hrs 15mins
Lille: 50mins
Lyon: 2hrs
Le Mans: 1 hr 30 mins
Marseille: 3hrs 30mins
Nantes: 2hrs 50mins
Rennes: 3hrs
Tours: 2hrs 30mins
Valence: 2hrs 20mins

Amsterdam (Schiphol) to:
Amersfoort: 40mins
Antwerp: 1hr 40mins
Den Haag: 30mins
Groningen: 2hrs 30mins
Osnabrück: 3hrs 15mins
Rotterdam: 45mins

Frankfurt (Rhein/Main) to:
Baden Baden: 1hr 20mins
Karlsruhe: 40mins
Kassel: 1hr 40mins
Koblenz: 1hr 15mins
Mannheim: 40mins
Nuremberg: 2hrs 30mins
Würzburg: 1hr 40mins

Geneva (Cointrin) to:
Bern: 2hrs
Lausanne: 45mins
Montreux: 1hr 10mins
Neuchâtel: 1hr 30mins

Zürich (Kloten) to:
Basel: 1hr 30mins
Bern: 1hr 50mins
Intelaken: 2hrs 40mins
Lucerne: 1hr 15mins

Copenhagen - Kastrup to:
Aarhus: 3hrs 30mins
Gothenburg: 3hrs 10mins
Kalmar: 3hrs 40mins
Odense: 1hr 50mins

Oslo - Gardemoen to:
Lillehammer: 1hr 30mins
Trondheim: 5hrs 50mins

Stockholm - Arlanda to:
Gavle: 1hr
Linkoping: 2 hrs 40mins

Lyon - St Exupery to:
Chambery: 1hr 5mins
Grenoble: 1hr 5mins

Bruxelles - National to:
Gent: 1hr 25mins