Be glad you were invited and make something!
- 7 layer dip (salsa, cheese, refried beans, chilis, sour cream, guacamole, etc) there must be another layer?! and a bag of tortillas, either bring it already hot or put in the microwave once you arrive.
- spinach dip (use Knorrs mix) in a hollowed out round bread and bagel chips / crackers
- vegetable crudites with dip
- fruit salad (extra points to serve in a hollowed out watermelon)
- greek salad (dressing on the side)
- pasta salad (make dressing with balsamic vinegar and olive oil, salt & pepper or a creamy option: ranch dressing) then chop up all kinds of stuff that's in your produce drawer - peppers, tomatoes, onions, celery, peas, brocoli florets, etc - add some pepperoni, cubes of cheese or ham, or chicken, and you're good to go.
There are so very many easy dishes to bring I'm sure you can find something!