Hiking is the most amazing fat-burning I've found. At my current weight of 264, I burn more than 1,000 calories during an 80-minute cross-country hike (and I hike three times that amount at least twice a week). That's insane. Yes, I realize those who do cardio machines at the gym may already be aware of how intense this calorie-burning thing works, but I could just never get into machines. Hiking hills close to home is the only way I'm going to be able to overcome obesity once and for all. Thirty-seven pounds to go!
If you're interested in calculated the number of calories you can burn by hiking, according to your current weight, check out the hiking fitness calculator at Self Magazine.