I travel a lot also, sure makes it a pain in the rear. The Delta Sky magazine has had a few interviews and articles about this in the past year. They kind of summarize that you're not going to get a "weight training" workout but that you can maintain and do some cardio at the same time. Here are some of the exercises they've mentioned:
-Burpees come up a lot. Good for legs, core and cardio.
-Zero weight squats - do them till your legs turn to jello
-"Dips" if the room's chair has arm rests (and that their strong enough to hold you up). Your feet are still on the ground and they do hold some of your weight, so you're doing higher reps vs. a real dip where you're lifting your whole body weight
-obvious pushups and sit ups
-lunges
-"touch down" (not sure that's the right name). Stand feet a bit wider than shoulder apart, hands up, palms out about parallel with your face. lean over to your left and touch your right hand down (not finger tips, your whole palm has to be on the floor) about six - eight inches in front of your left foot. Now do the right, do a jillion of them. Your definitely using your legs, hips and core on this one, NOT just bending your back over, focus on legs and butt.
-pilades moves. YOu can youtube and follow along.
Working out and eating right on the road is really tough but I do see people doing it right. Eating is the biggest issue and more chains are offering bunless burgers, more substansal salads, all day omelets, etc.. Good luck!