Here is
-ANOTHER- helpful link. It is a very inclusive "calories burned" calculator. What I like about it is that you can input your specific data and the activity list has just about every activity you can think of.
For hiking, I generally use the time function and additionally the nifty feature that allows you to add together multiple activities so I can break it down and be real specific. For instance, lets say I take a hike and it takes me 4 hours to reach the summit, 1 hour lounging on the summit and 3.5 hours to walking out.
I'll enter my data - (M/38, 5'11", 191 lbs) and then the activities;
- 4 hours @ {Hiking - climbing hills, 21-42 lb load} = 2787 cals
- 3.5 hours @ {Hiking - cross-country, general
**} = 1829 cals
- 1 hour @ {Socializing - sitting (talking, eating)
}
for a total of 4,747 cals over 8.5 hours.
** - considering the significant difference in physical effort going downhill, I use the general activity for decents. 
