I have a very long lay-over in Paris at the end of may. I arrive in Orly field at 4pm and leave out of Charles de Gaule the next morning at 11:15am. My question is where to stay? Should I stay close to the CDG airport or close to Champs Elysees, etc. Also any reccomendations on where to eat and what to see if I only have one night? I've never been to Paris before.

Wow. One night in Paris, I'd be tempted to stay up all night, walking around!

I would take the train into Paris and stay at the Hotel Select. You can find it on the web. The hotel is easily walkable from where the train lets you off (unless you have a lot of luggage). From there, I would take a Batobus up and down the Seine if it's still running at the hour you arrive, otherwise I would try to find a commercial cruise to take. If you can't find a boat, walk along the banks of the Seine, the Ile St Louis, the Ile de Cite.

A walk up and down the Champs Elysees at night would be great fun. Of course all this assumes it's not raining. If it's raining, take a cab to Le Dome and eat oysters and watch the world go by. There are many late night clubs you could go to if you'd like that.

There are only a few areas of Paris where it is unsafe to go at night. Have your hotel desk point them out to you.

But I honestly have to say that what I might very seriously consider doing is checking my bags through to my next flight at the airport and just staying up all night in Paris, to see the sun come up.

Oh, and PS: With the money I saved on a hotel room, I would treat myself to a 4-star meal in a world class Parisian restaurant.

I agree with nessundorma, go into Paris. It's so easy to get to and from the Airport it'd be a shame to be so close and not see Paris, if even for a few hours.
As far as hotels, it depends on your budget. There are many budget hotels in the Latin Quarter. We've stayed at the Senlis a few times and have found it to be clean and quiet. It's near the RER Luxumbourg station which takes you right to CDG.
What to see? Once again, I agree, walk along the Seine, walk, walk, walk. Have a metro map with you and you'll never be lost. Paris is gorgeous at night (i.e. the City of Lights) and there's always something going on.
Stop in a cafe for a drink, eat a crepe from a little creperie where it's just a window you walk up to and order, be thankful you get to experience such a wonderful place, if even just for a day!
Oh, and please learn some French phrases. even if you massacre the language, the people will at least appreciate that you are trying to speak their language... since you are in France, after all.

Gosh. I would stay near the Champs-Elysees. You're arriving early enough to enjoy promenading down the street toward the Carousel (after seeing the Arc du Triomphe). Assuming the timing goes well, I would head down the Champs to the Louvre (you'll pass gardens and walk right through the Jardin du Tuileries) and hot-foot it up to see the Mona Lisa. There is much more impressive art and sculpture on the way to that display. (Hint: at the top of the stairs, go left through the hall of Grecian statuary. It's much shorter than going through the entire Italian/Spanish section.)

After that quick trip, I would mosey back up the Champs to the Grande Palais, pass it, cross the river toward Musee D'Orsay. Then follow the river up to the Eiffel Tower. Even if you don't go up, it's quite a sight. The night lights can be lovely and the view of the city from the overlook is gorgeous. From there you can trek back toward the Champs-Elysees and pass over in the direction of the Opera Garnier if you like. Or you could just meander along the river down towards Notre Dame, etc.

You can eat sumptuously or just grab something at a boulangerie. I had a chicken sandwich that restored my faith in sandwiches. It was unbelievable.

If you do stay in Paris, why stay close to the Champs Elysees? Stay closeby to Notre Dame, the Marais, or even better the Ile St. Louis. The Champs Elysees is nothing but a large touristy street containing fast food restaurants, touristy restaurants, and stores. It is not charming in my opinion.

Hi beej,

If you are young enough, I ditto nessundorma.

Take the RER B to Gare du Nord.
Check your baggage.

Spend the night seeing Paris.

Have breakfast, collect your luggage, and take the RER to CDG.