I'm not marathoning quite yet, but I do run daily, so I've been adopting a slightly more activity-inclined diet. I usually eat a carby snack in the morning, (lately it's been a piece of whole wheat toast with a sliced banana with cinnamon sprinkled on it) and that fuels my run. Then I shower and get ready for the day and eat the rest of my breakfast. (Smoothies lately. Soymilk, lots of ground flax, blueberries, and whatever else is lying around.)
      As far as the rest of my meals go, I love whole-wheat wraps with steamed veggies (as many as will fit) and HUGE scoops of hummus.(Trader Joes is pretty tasty for store bought, and lower sodium than most. It comes in organic now too.) I like looking for non-soy protein sources, because I'm kind of a tofu and tempeh addict; hummus is still carby (unlike tempeh/tofu), so it's good for runners. I also eat massive amounts of green peas; again, starch and protein. (And I'm in love with them. But that's another issue.) I use my stove-top steamer for just about every meal. It'll warm pretty much anything nicely, and doesn't use the oven. (If you don't have one, definitely pick one up. The Chinese bamboo ones are fantastic, and cheap.) Then I generally toss whatever I steamed with either nuts or a cold sauce, like salad dressing, salsa, or my own random concoction. Nut butters and pasta sauce can be pretty tasty if mixed in the right proportions. Sandwiches are natural hot weather options of course, as are stir-frys and anything else that can be done quickly on the stove-top.
  Wow, I can't write anything without it turning into a novel. Basically, eat lots, and eat often, which you're already doing anyway. :P I've not really said anything useful, but I hope it helped anyway. Good luck with your training!