A small salad, careful with the dressing and/or veggie sticks (carrot, celery, etc.), a small fruit or small baggie of dried fruit, and half a sandwich (meat and cheese).
An alternative is to have a heartier salad with some steak, chicken, or nuts, cheese, and crutons instead of a sandwich and some fruit.
Another is a pasta salad (cold pasta; walnuts; tomatoes, peppers, spinach, other veggies), fruit, and a small yogurt.
A fourth, and the easiest to make, is to throw some triscuit, a baby cucumber, carrot sticks, a small handful of nuts, and either a small yogurt or a cheese stick.
All of those are ideas for easy to pack lunches, and based on what I make myself. I don't eat a lot of meat at lunchtime, so ideas with those don't really come to mind.
I consider healthy having a balanced lunch, so I try to get dairy, protein, fruits, veggies, and grains in it. I usually get full pretty easily. Depending on what dinner was the night before, sometimes it can be a good lunch. I don't know if you mean to eat at home or to pack though.