My trips to Nepal, Patagonia, Peru and Africa were organized Adventure Travel "Treks" put together by Mountain Travel * Sobek and KE Adventure Travel.
The term "Adventure Travel" might not be familiar to some, and might mean something entirely different to some people than it means to me, so I should clarify it in my own terms.
First and foremost, Adventure Travel almost always gets you into unusual places and activities. You will not be relaxing at a resort or spending a great deal of time in any place regarded as "civilized" by most people. Quite often that means the accommodations are primitive (read tent!) and the transport unusual (read horses, yaks, rafting or on foot!) This is not for everyone, but on the plus side you get unparalleled opportunities to see exotic and truly spectacular places such as the Himalayan mountains.
The ways to do this kind of travel range from venturing out on your own to organized treks put together by tour companies specializing in this sort of travel. Personally, I prefer the latter, since I need to have reasonably well defined periods of time to be absent from work, and the better adventure travel companies can bring such a wealth of knowledge to the subject and provide such excellent guides that a trip which would otherwise be uncomfortable or outright dangerous becomes safe and a great deal of fun (if somewhat arduous).
The kind of trips that I prefer are lengthy walking trips, hopefully a circuit of an area rather than a route that you must backtrack on to complete the trip. The trekking company will organize the trip such that you almost never have to carry more than a day pack with some extra clothes and your camera. Details of transport vary, as we will see on my trips. The disadvantage of this method of adventure travel is a partial isolation from the culture of the area, as you depend a great deal on your guide and organization instead of finding your way yourself. In spite of the organization though, you cannot help but experience the culture, especially when things go wrong; and they will go wrong, thus putting the "Adventure" in adventure travel! We get so very used to the convenience and dependability of travel in the United States and Europe that we forget that it is not like that in other parts of the world. It gives you a respect of and tolerance for other cultures that is perhaps the most valuable lesson of adventure travel.