First I want to suggest NOW as the BEST time to get in those trees (decorative and fruiting) and shrubs in the ground. They're going to need a few weeks of watering right now... but then they will go dormant and won't need the deep watering like they would need in the spring while waking up.
Secondly, if you have bulbs, crocus, iris, tulip, ect. Its time to dig them up and split off new bulbs to transplant as well. (Or give away when you have too many)
I found some really great detailed suggestions over on The Master Gardener Website. Read up, and do your chores.... Spring will be a lot let stressful!
Master Gardener Website Link
Here I have my daughter helping me turn compost into a raised bed... this bed will house some garlic and onions for harvest next summer.
Please feel free to comment with some suggestions and things you do in fall to get ready. I've only been gardening for 2 years now, and I bet there are things we could all be doing more efficiently... especially me!