I've had several friends that are either auditors, or general business consultants. They do seem to get a lot of travel in, etc. I would also say people that are software/hardware installers, or work on projects for mid/major softare deployments, etc. For instance, our company put in an ACD (automatic call distribution) reporting system, and it involved two to four trips on the part of the company. Both to do planning, installation, training, etc. Oh yes, speakers and trainers would get a lot of travel in as well. Then you would have freelance or IT consultants with firms, etc. Or if you work for a company that has offices around the country or world, etc.