Day trips from Paris

Versailles!

Chateau de Pierrefonds in village of Pierrefonds and you can visit the Armistice Museum nearby....spent 2 days there last September. North of Paris and east of Compeigne.

In addition to Giverny, my must sees are: Versailles, Vaux-le-Vicomte, Fontainebleau, and Malmaison. Chantilly is also very nice.

I second al places already mentioned, they are certainly worth a visit. I also want to recommend the Vexin region just north of Giverny. Lovely countryside to explore with numerous nices villages like Ambleville, Lyons-la-Forêt and many nice views.
Between Mantes-la-Jolie, 50km west of Paris and Rouen the Seine is surprisingly scenic. 9km Before arriving at Giverny have a stop at Château de La Roche-Guyon. Further to Rouen from Chateau Gaillard spectacular view over the Seine. Best is to use a well detailled map with a 1/150.000 scale for driving around, otherwise you get lost. This kind of maps (Michelin, Departements, yellow cover) give also usefull touristic information and suggestions for itineraries. May is perfect for this kind of trips.

Chantilly is easily to combine with a visit to Auvers-sur-Oise, where Van Gogh lived.

I love visiting Peirrefonds.. but there is no train there.. we have always gone by car. There is a way to get there by public bus or taxi from nearest town but I am not up on that ,, there are posts about how to get there that way on tripadvisor.com Paris forums though..
Chantilly is lovely and never crowded, but since you only have 6 days I think Giverny and Versailles is more then enough out of city time. !

We went to Provins, a beautiful little village outside Paris. You take a commuter rail about 40 minutes to get there (I think from Gare de l'est, but please confirm). It was an easy way to get out and still be close to Paris. There is nice hilltop fortress and church. This was an important trading/fair town during the Middle ages. You can easily walk from the station to the town center.

Chartres! Beautiful little town...and of course, STUNNING cathedral! Surrounded by nice countryside too!

I second Chartres. It's an easy daytrip via train from Paris and aside from the Cathedral, the town itself is worth seeing.

Check out post 6 of http://www.tripadvisor.com/ShowTopic-g187147-i14-k6470251-Day_trips_from_paris-Paris_Ile_de_France.html#49309885.

In this long list of day trips from the TripAdvisor post they recommend St. Germain-en-Laye... I grew up there and I love it but I wouldn't recommend it to someone who has only 6 days in Paris and hasn't been to the places recommended in the posts above. One of the things I like about the RS forum is that answers here are supposed to be based on personal experience.

Susan I understand your point,, but that list on ta by the poster Frenchmystic,, he HAS done all those daytrips.. and has many photo essays to back it up.. He is an American who married a french lady and is living just outside Paris .. he started taking tourists on private bike tours a few years ago and now has a thriving business.. but originally he started exploring by bike just for his own amusement and then decided to do the tours .. ( I have followed his posts for at least 4 or 5 years now.. on ta and on another forum).

Hi Pat, but that's French Mystic's personal recs and I doubt he'd recommend St. Germain-en-Laye (and others on the list) to someone who only has 6 days in Paris and hasn't been to Versailles, Chantilly, Fontainebleau, etc. I think answers should be geared to the op's situation, not just a list of day trips from someone else. You and I could easily list every day trip there is... : )

I went to St Germain en Laye on a market day last trip and enjoyed it much more then Chartes. Not sure why Susan is so determined to discourage visitors. Perhaps because she grew up there it is boring to her, but I loved it and hope to return.

Carol, I said I love St. Germain-en-Laye.

In case it is an issue, I have been to the places included on the list that I linked to as day trips. I could have listed them all but remembered the post from and thought that it might be useful to the OP to have the list and the links to sites and not just my list of possible day trips. In the interest of clarity, I was answering the "what else is accessible" question as opposed to opining on must sees.