My roomates and I did this throughout college. Nothing like someone cooking a japanese style curry with some veggies for like $1.50 total cost to me. I would usually do chili to contribute.

Nowadays I have enough money that any time I want to grill something big (a lot of burgers, some whole fish, a rib roast, etc.), I invite a bunch of my friends for a free meal.

Maybe try volunteering to cook for a soup kitchen near you though. They kind of specialize in large scale cheap but filling recipes.