Kraft makes a version of Easy Mac packaged in a styrofoam bowl...just add water up to the line and zap it for 3.5 minutes. I'm not a big fan of mac n' cheese, but they also make it with Italian pasta and fettucini alfredo. Those aren't bad. Lots of carbs and sodium though.

Otherwise I pack trail mix, muffins, fruit cups (and applesauce), StarKist tuna salad kits, beef jerky (the real stuff...low fat...not slim jims), soup, crackers, granola or yogurt bars, oatmeal, and lemonade powder.