A really easy and tasty way to make up a pasta salad is just to boil some pasta (say the shell or twirly shapes), rinse in cold water and drain. Add the contents of a jar of ready made pasta sauce (Tesco's do a nice own brand range, the mushroom or the chilli - mild - ones are really good), just enough to coat the pasta. Great served up cold and even more filling if you use the wholewheat pasta rather than the white.
For slightly different sandwiches, how about a pitta bread sliced open, spread some chilli hummus and a bit of shredded iceberg lettuce and cucumber (that's got protein, carbs and vitamins !) Or you could spread some bean pat� onto a tortilla wrap, add some thinly sliced tomatoes and a few bean sprouts or very thinly sliced red peppers for extra crunch.
I often make up a (veggie) quiche and take into work a slice of that, plus some pasta salad, some rice salad (cooked brown rice, peas, sweetcorn and chopped peppers in a very light vinaigrette sauce), a bit of home made potato salad and then a fruit yoghurt for pud...