Research. Check out your space and find out what the hotel has to offer.See if you hotel supplies yoga mats. If not, a thin mat is easily packable and takes little room. Yoga mats are perfect for stretching, pushups, sit ups and, yes, even yoga.
Check your TV. Sometimes your hotel network will offer exercise programs on demand that you can follow in your room. Does your room have a DVD player? Workout DVDs are easy to pack, inexpensive and can provide great exercise!
Even with zero equipment, you can get a decent 30 minute workout. Buy a fitness magazine in the hotel gift shop. Almost all publications offer at home exercises that can easily be adapted to your hotel room.
Take the time to develop a travel workout according to your needs. Three sets of 15 lunges, sit ups and push ups is a great start. Add leg lifts, crunches and yoga poses to increase the difficulty and variety.