An idea that works great is to keep a bunch of salad bar-type ingredients in a specific set of refrigerator containers (Tupperware, Lock&Lock, etc.) that you use just for your "salad bar."
You can boost the flavor and nutrients of lettuce by adding:
Beans are always good:
Fun add-ins to go with your salad staples (celery, tomatoes, etc.):
dried fruit (cranberries, cherries, sour cherries, raisins, golden raisins, strawberries)
fresh fruit (mandarin oranges, apples, blueberries, raspberries, strawberries, mangos)
dried veggies (crunchy and better for you than croutons)
olives--black and green
marinated artichoke hearts
marinated or baked tofu
Nuts add protein and crunch:
sliced or slivered almonds
Have fun with your salads and let us know your favorite combinations!