this is the original Kellogg's recipe - I always have to look it up online, so I figured I'd stick it in here for easier finding
3 Tbsp margarine
10 oz marshmellows
6 cups cereal
In saucepan, on low heat, melt margarine. Add marshmellows, stir until smooth.
Remove from heat, and add cereal. Stir to coat, and spread in a greased pan. Cool and cut into squares.