Kano: like everyone said it's pretty much a personal thing and you'll have to try some different things to see what works for you, and try eating at different times to see what's best for you. On long rides I carry PB&J on rice cakes but just recently a friend of mine had one of those packages of cheese crackers and it was Just what I needed to finish my ride. I try to make sure I have a carb and a protein (trail mix is a great idea) for my bike food and that I eat a good breakfast before I start. In my case it's usually an egg white omelette, a veggie - usually tomato, and a fruit. If I'm going to do a long ride that day I may include 1 yolk in the omelette just for the fat.
the best suggestion I ever got came from right here on the board: try and finish off a bottle an hour and try to eat at least every hour. and listen to V - even if you're close to finishing your ride, if you're feeling hungry or parched, stop and eat/drink, don't try to finish the ride first coz (speaking from experience) you're just asking for trouble!
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"