In reply to ewar woowar:
I'm a one-pot guy.
Yes a lid helps (should save about 10% fuel), so does insulating the pan walls, actually an equally large surface area. I use a cut up fire blanket, which means I can hold a boiling pan safely in my bare hand, and it can stay on the flame and will never burn.
As above, you can make your own lid if you don't want to carry something heavy, but mini frying pans are good, and more practical (you can cook in it and eat out of it) than just having foil, or a lid without a handle.
The vitamins (mostly vitamin C) comes out in the water when you boil veg, so you really should drink that (or recycle it) into a broth or something. You've spent all that fuel and energy heating up water, and carrying friesh veg to cook, so why not utilise it?
I tend to use oil, it's higher calorie and faster to cook, and if you use a nice oil (infused) then adds flavour too.