The main staples for DD1's lunches are:
Choc Banana Muffins (Nigella's recipe)
Bacon & Zucchini slice done in muffin tins
Veggie sticks, apple slices and hommus.

I often try to work out what I can do with dinner leftovers for lunches:
Cut up sausage, cheese, veggie sticks and sauce
Sausage sandwiches
Meat and veggie fritter (diced veg and meat in a fritter batter) cut into fingers for dipping in sauce
Homemade pizza
Homemade cheesymite scrolls