Can act as a natural mulch.
Help retain moisture in the ground.
Provide a warm winter blanket for insects.
Provide a natural fertilizer when they break down.
Add a few inches of leaves around landscaping plants to protect them over the winter.
Add a layer to your vegetable garden to enrich the soil over the winter and suppress weeds.
Keep a pile of leaves to slowly break down and form "leaf mold". This organic matter is great for adding to your garden.
Keep a bag of leaves next to your compost bin to mix in periodically with food scraps and garden clippings.
Mulch the leaves with a lawn mower to help them break down and fertilize your lawn.