Carbona makes a product that takes off gum - it is part of a series of stain removers they put out. In the laundry aisle, it will be in a tiny yellow bottle about 3 inches high, and I think it is actually called gum remover.
It got gum out of my DH's wide wale cords that had been ground in and you can't even tell it was there. I would caution against peanut butter - I know it has technically removed gum for some people, who have then ended up with a grease stain from the peanut butter on the fabric instead!
Jane