Airline flight crews, military, photo or print journalist, nature photographer. The people that do the most travel in the company I worked for are supplier management people - particularly auditors. With globalization, a lot of supplied parts, materials and subassemblies come from far flung places around the world. Some of the people I used to work with traveled to Germany, China, France, Mexico, the US, Korea, the Czech Republic and other places around the world frequently.
You need to be aware that traveling for a job is not the same as travel on a vacation; it can be a great opportunity and rewarding. It can also be a lot of wear and tear - you really have to have the right personality to be on the road a lot and you don't necessarily get a chance to spend any time sightseeing.
Other possibilities might include oceanography, anthropology or archaeology but they don't necessarily get you in the field.