What are foods with gelatin in them?

I am always looking for foods that contain to gelatin at the store to make sure I don't eat it...but when I look at something, EX: Margarine, at the store it doesn't say it as an ingredient, but on websites it says margarine does have it. If you know a list of foods with no gelatin, and foods with gelatin, please let me know! Anything will help! I know yogurt, skittles, and starburst have gelatin, what else? Does all margarine? HELP!