... there's a book I'll recommend. An acquaintance of mine wrote it, and it's been selling well. It's about how to workout with virtually no equipment, using bodyweight and household / hotel room furniture. There are two or three exercises that would require light dumbbells, or similar, but the vast majority of exercises in the book require little more than the right attitude.
http://www.marklauren.com/
For background, Mark is a former USAF Combat Controller, who helped design the fitness program currently in use by the Air Force for Combat Controller training. You can find reviews of the book pretty easily via google, and even those that criticize Mark's writing style seem to praise the actual exercises.
And the really nice things about it, in my opinion, are:
1) As noted, you can do most of this stuff in your home, or at your hotel when on business. You don't need a gym, or special equipment; and
2) Mark has provided ways to increase difficulty for each exercise; he has also set things up to allow design of effective 20-minute workouts.
I have a signed copy, and I highly recommend the exercises in the book.