I found that two small breakfasts did me well while commuting. Pre-ride I eat a piece of fruit, nothing heavy at all. After I get into work and shower I have a larger meal (but still not large), usually with some carbs like a bagel or something. I have to bring a bigger lunch, with bags of snacks so that I can spread the lunch over a few hours. I'll bring yogurt, carrots, nuts, a sandwich, an apple. I'll usually eat the fruit or yogurt around 11, then the rest during regular lunchtime, i'll eat whatever is left around 2 or 3 to give me some fuel for the ride home. If it's hot out, I buy a gatorade or mix up some cytomax (I have a container in my drawer at work) and start hydrating a few hours before riding home. I do feel like I'm constantly hungry when I commute, though. I guess it jumpstarts my metabolism.
K.