We will be coming back to Paris from other parts of Europe the day before we're to leave for home. The inter-europe flight we have goes into Orly Sud and we fly back to the US out of CDG.

Where would you stay? Closer to CDG? In the heart of Paris again (we'll have another day and night of sightseeing before our departure). What would be most convenient?

Thanks
D

if your flight gets in pretty late you may want to stay near orly just for that night. but if not...
i'd suggest staying at a hotel in the 5th/6th, close to the intersection of bd.s st germain and st michel. payoff: the RER B line that takes you straight to CDG is there. the hotel we like is 3-4 blocks from the st michel stop:
Hotel Saint-Pierre
4 rue Ecole de Médecine, Paris 75006
2 star w/ friendly, helpful, english-speaking staff. they are under revovations right now but it shouldn't be an issue unless you sleep late or take midday naps.
and i don't need to mention this is an awesome neighborhood to stay in! i highly recommend it, even if your preference is the marais, etc.
have fun! (and do a picnic lunch along the seine or in a park at least once)

A taxi from Orly to Paris is about 20-25€. If you have that much time, get a Paris hotel and enjoy the time.
You also might be able to take the Roissy bus from Orly to Invalides and get a nice reasonable hotel in that area.

There is no Roissy bus from Orly to anywhere, the name Roissy refers to the area where CDG airport is.

There is an Orlybus that goes from Orly, but it doesn't go to Invalides (the Air France bus does that) -- the Orlybus goes to Denfert metro/RER stop, which is fairly convenient. There are RER connections from Orly into Paris, also.

It would make more sense to stay on the Left Bank -- actually, the bus to Denfert sounds like a reasonable idea, there are several budget hotels around that location (like Hotel de Midi or Sophie Germain) and that is a pleasant area but not that far from Orly (at least in the right direction).

If you settle in to a hotel there, you can easily take the metro or RER to the Latin Qtr or Montparnasse, or just stay around there. Here are some mentions of the hotels I'd consider myself:

Sophie Germain
http://www.paris-tourism.com/hotel/us/520.html

(it's also on www.venere.com and I thought had its on URL but can't find it )

www.hotel-midi.com

You know, I was thinking you were arriving and leaving from Orly -- but Denfert would actually probably work in either case as it's right on the RER B line which goes directly to CDG. So you can get there by the Orlybus and leave for the airport on the RER.