Incidentally, it takes about 30 minutes to bake enough granola to last one person two weeks (and homemade granola is miles better than anything you can buy in a store). Get a bread machine and you can make your own bread from scratch quite easily, too; depending on how much bread you eat, a $80 machine should pay for itself in a year or so (figure about $1/loaf for homemade bread vs. $3-4/loaf per store-bought).
My usual lunch is a peanut butter and pickle sandwich (yeah, I'm a freak) and an apple. On days when I fail to prepare my lunch and have to eat out, I definitely notice a huge difference in my alertness in the afternoon, pretty much regardless of where I go. Not to mention it's costing me many times what the homemade lunch does.
Granola recipe:
5 cups rolled oats
1 cup sesame seeds
1 cup sunflower seeds
1 cup whole wheat flour
1 cup wheat bran
1 cup crumbled/chopped walnuts
1 cup canola oil
1 cup honey
1 cup dried cranberries
Mix together dry ingredients (not counting the cranberries). Heat oil
and honey on the stove to mix them, then mix in with the dry
ingredients. Add any spices at this point (cinnamon, etc. -- whatever
you add, you'll need a lot!). Bake on a cookie sheet at 350°F for 30
minutes or until golden brown. Remove from oven, pour into a fresh
mixing bowl. Mix in cranberries, allow to cool.
That's it. Very simple. Moreover, it's very experimentation-friendly and you can be pretty sloppy putting it together (nobody's going to notice if you accidentally put in 1.5 cups of sesame seeds, or forget the walnuts, etc.).