Rake Out Leaves from Under Shrubs and Around Perennials
Yes, chopped or composted leaves break down into good nutrients for garden soil. Whole leaves, not so much. Matted on and around perennials, they can smother the crown by holding moisture and reducing air/light. Clustered in low shrub branches, whole leaves are inviting havens for non-beneficial insects to overwinter. So rake them out.
Use Leaves To Suppress Weeds
Are there unplanted areas in your garden where weeds take over all too quickly? Whole leaves make good, weed-suppressing mulch in this situation. Pull out as many weeds as you can. Heap on leaves raked from your yard -- a layer 6 to 8 inches deep to start. They'll clump to form a thick mat for winter into spring. The more leaves, the thicker the mat and the longer they'll last into next summer as a mulch cover.
Use Leaves to Top a New Spring Bed
Is there a spot where you'd like a new garden bed? Get a head start on spring bed preparation by heaping leaves (8 to 10 inches or more) on that area. Great if you lift off the grass with a square-edged garden spade and pull the weeds first. Then rake on a huge mound of leaves. They'll decompose over winter. Come spring you'll find it easier to turn the soil AND you'll be improving the soil with leaf mold nutrients.
Remember Spring-Flowering Bulbs
It's best if bulbs are in the ground by Thanksgiving at the latest. They need to push roots and get established before the soil freezes for winter. Get yours in the ground as soon as possible.
Do NOT Cut Back Lavender, Grasses, Butterfly Bush Now
Though it's ever so tempting to prune away at the overgrown butterfly bush, do so sparingly if at all. Removing seedpods is recommended. Pruning off a few branches that are in your way is okay. Wait till you see green next spring before doing substantial cutback though. Premature pruning a lavender or butterfly bush (before winter) will likely mean no regrowth in spring. Allow ornamental grasses to wave in autumn breezes and winter winds. Clip them back in spring, when green sprouts poke out at the clump's base.