Best Way to Keep Digital Camera Lenses in Bag?

What's the best way to keep your digital camera lenses in a medium or large camera bag - in a case they came with or by themselves all packed together in a compartment inside the bag?

i have a bright yellow, what looks like a lunch box, case. inside is foam which squeeses the the camera in place when i close it. there's plenty of room for cards, batteries, a charger, and if i dropped it, nothing would break.