"The entire JMT requires the use of a bear can and I would be very impressed if you can get 12 days of food into one."
Darren, this is not quite right. A bear canister is required on some parts of the JMT, but not others. Anyway, it's a moot point for someone like Craig who is not resupplying, since he's going to have the same equipment all the way through. And in any case, you make a good point that energy per unit volume may be even more important than energy per unit weight.
Tom's suggestion of olive oil is a great one. Olive oil has twice the energy density of a granola bar! You can buy it in single-serving foil packets ( http://www.minimus.biz/Dressings.aspx ), although the price may not be compatible with Craig's budget. I've brought pesto, and it keeps very well, but the energy density is not as high as for pure olive oil.
Ghee is another extremely energy-dense food. You can make it yourself from butter, so it's not too expensive. Basically anything with lots of fat in it is energy-dense: oils, nuts, ... I know a lot of people take an entire plastic jar of peanut butter, but that would bore the heck out of me, and you need something to spread it on. I prefer plain, shelled nuts, because I can get a greater variety of flavors.
Craig, what's the reason for not doing resupply? Do you just want the experience of total solitude? Or is the challenge of doing it without resupply what appeals to you? Otherwise, you can certainly stretch your calorie budget by, e.g., buying a double cheeseburger and fries at Tuolumne, ice cream and candy bars at Reds Meadow. Both of these are right smack-dab on the trail, no detour required.
Maybe I'll see you on the trail. I'm going north to south, second half of July. Have a great trip!