When flying, for example, I might book myself for two hours of focused work on project documentation, like the project plan or strategy documents. If I'm stuck waiting for a connecting flight or in my hotel room, I use that time to catch up on emails.
Traveling is also a good way to network. Try to connect with people who might help you resolve project challenges or look at issues in a new way. You might even want to find out how they stay productive while on the go.
As a project manager or a team member, I can still be in action and engaged in the project -- no matter where I am. Is traveling a hindrance or a non-issue for you? How do you stay productive yet balanced during your business travels?