I like to make cold macaroni salad dishes like tuna/mac and or chicken/mac. I use half mayo and half plain yoghurt to reduce the calories and cut up some onion and celery as well. Mix well, season to taste...
I've also started taking deviled eggs to pot lucks, they go really fast, are pretty easy to make if you know the quick shell routine: cook 'em, put 'em in ice water till they are cold, knock 'em against the sink under running water and they peel beautifully.