Lightly grease a large roasting pan; stir in cereal or crackers, popcorn and peanuts. In a saucepan over medium heat, mix together brown sugar, butter and corn syrup. Bring to a boil and cook, without stirring, for 5 minutes. Remove from heat; add vanilla and baking soda. Mix well and pour over mixture in roasting pan; toss to coat. Bake at 250 degrees for 45 minutes, stirring every 15 minutes. Cool completely; add candy, tossing to mix. Store in an airtight container.