My husband and I have a 12 - hour overnight (10 pm - 10 am) layover in the Lisbon airport. I understand there is no hotel inside the airport. Is there anywhere in the airport to stay overnight that doesn't involve stretching out on the floor?
Should we get a reservation at a nearby hotel, and will we be able to get to/from the hotel in time for our check-in the next morning?
We'd appreciate suggestions!

http://www.lisbon-airport.com/, this gives a little overview even if it's outdated, the airport is now connceted by metro too, I would book a nearby hotel, worst case you have to take a taxi in the morning.

Check booking.com and type 'Lisbon airport' in the destination field.
I found the Holiday Inn Express for 59 € for a double room including breakfast and shuttle service to the airport.
Have fun !

You got 8 hours so why not enter the city for dinner and explore it a bit?
http://www.flickr.com/photos/youngadventure/sets/72157632246049955/