Leaves layered into black polythene sacks and then left for several months will turn into an enriching leafmould!
The leaves of trees and shrubs can be rotted down on their own to make soil-enriching leaf mould! Or you can just add them to the compost heap. You can even make your own leaf mould bin: make a nice wire container from chicken wire stretched between four upright posts that have been driven into the ground! To save space you can pack layers of leaves into black polythene sacks perforated so that they let in air. Tie them at the top and let them stand in out of the way places where they will make your free leaf mould for you. From: Organic Garden Basics: by Bob Flowerdew.