Hotel for Paris Day Trips?

That's not such an easy question.

Paris, like London, has many main stations which serve particular areas.

No one location is best for all.

Montparnasse for example is the station for Chartres, and Gare de Lyon, Nord or Est for the TGV station not particularly near Reims - although Est is the direct one (the others need connections), unless you want a milk run.

Each of the Paris stations is easy to reach from most parts of the city by Métro and/or RER.

Don't forget the "r" at the end of Chartres (shar-treh) - otherwise it sounds like a nasty mess. {that Rick Steves episode makes my students die laughing and I try to cover it up by saying the final "res"

With the metro, Paris is so easily accessible. If you feel youre going to be seeing more of Normandy / Chartres / Rambouillet / Maintenon stay near Montparnasse. I like the 14th.

Thanks for all the good advice. It is appreciated!

pick a nice reasonably central neighborhood so you have a nice place to stroll in the evening when you get back from day trips -- as others have noted there are half a dozen train stations and they serve different sectors of the country.

Convenient departures can benefit from another sort of train -- the Metro. I like the area around Place de la Republique because its Metro station is on five different Metro lines. Your day-trip departure locations should be easily reached by one or more of them. Plus the Place de la Republique is a central forum for the city, swarming with skateboarders and ballroom dancers and the not-infrequent political demonstration, a traditional form of Parisian street "theatre".