Hmmm... Mojo bar from Cliff is a good choice. I buy these in bulk ever since REI sent me a free sample...

http://www.clifbar.com/eat/eat.cfm?location=mojo

It tastes much better than any health food/energy snack. It has its own uniqe flavor that will either win you from the first bite or you will hate it forever. It is priced better than anything yet not as cheap as granola bars.

Another thing is power-jel in bannana-strawberry flavor. That goo really tastes good and can be molded (while still in the packaging) to fit into any free space you have left in your bag.

Matt