Here's a simple one that you could scale:
2 cups elbow macaroni, uncooked
3/4 lb. (12 oz.) VELVEETA®, cut into 1/2-inch cubes
1/3 cup milk
1/8 tsp. pepper
COOK macaroni in large saucepan as directed on package; drain well. Return to pan.
STIR in remaining ingredients; cook on low heat until VELVEETA is completely melted and mixture is well blended, stirring frequently.
I've made it and topped with crushed gold fish crackers mixed with a little extra shredded cheese and cooked in the oven/smoker until bubbly.
Fireman_pete has recipe that I used at a summer party this year that got good reviews. It's where I stole the idea of the crushed gold fish crackers from.
There is also the google search of this site at the bottom of the page, lots more results there.