Rachael Ray is onto something when she says to prep your produce when you come home from the store. I love adding sauteed peppers, onions, and mushrooms to my egg dishes in the morning. It keeps you fuller longer and it adds a great flavor!
I am a huge fan of those Ziploc Twist N Loc containers (I have a whole drawer full of them). They keep the air out and keep your food really fresh for a long time! I dice up my onion, pepper, and sometimes my mushrooms and throw them into their own container. Then when I need something, it is all ready for me to use. I even sometimes saute the vegetables and then put them in the container. They keep pretty well for a couple days!