I am currently in Minneapolis for a a wedding, staying at the beautiful W Hotel, www.Whotel.com
A few things I never leave my house without are sneakers, workout clothes, resistance band and jump rope. Most hotels these days have gyms but just in case they don't.
You can always find a place to rope and if not, I have done it in my room.
You can do multi joint exercises with the band which I will demo when I get home. Also, just go to your floor, do crunches, leg lifts, push ups (my number one favourite exersize), squats and lunges....
Or, just get those sneakers on and go for a nice run or walk! Just move!