I throw in exercise at work wherever I can. A desk job doesn't permit much movement so in addition to Coach Nicoles exercises at your desk I have added the following: Jumping Jacks at the copier or while waiting for anyone or anything. Squats work also at the copier/fax. Use the stairs and get up and go to the persons office, don't use the phone or email. Lunges and squats while on the phone.
Add chair stretches!