My mom has cooked for almost all of our weddings... (over 300 guests for each of us) she always does pulled pork sandwiches and like green beans and some form of potatoes

She also cooks for the girl scout retreats a few times a year. We'll have between 50 and 120 kids each time. Here are some foods we've done...we always serve a serving amount and are on a limited budget.

spaghetti is a good option....

taco salad is a quick, easy, and can be fairly cheap to cook for a large crowd...

pancakes and sausage links/patties

sloppy joes

hotdogs

ugh... I know there are more...but I just can't think of anything right now.