Fall and winter are an ideal time to shift our focus to improving the soil for next year's garden. You want to improve soil texture, friability, water retention, beneficial bacteria/insects and fertility.
Here are some possibilities -
Plant alfalfa seed now and dig in the plants early next spring. Or, purchase bales of alfalfa hay and mulch the garden 3-inches thick. Alfalfa meal and pellets are available from feed stores, too. For use in a non-manure farm setting - https://www.mda.state.mn.us/en/protecting/sustainable/greenbook/~/media/Files/protecting/sustainable/greenbook2012/cropfernholtz.ashx
Blood meal from the slaughterhouse provides nitrogen. Alternatives for the squeamish include cottonseed meal and soybean meal from the feed stores. Bone meal is an old-fashioned slaughterhouse product that gets mixed reviews these days. Bone meal and blood meal are usually combined and added 2 pounds per 100 square feet of garden. See http://www.extension.umn.edu/distribution/horticulture/M1191.html
Worm castings are harvested from our worm bins a few times a year. If you don't have worm bins, please consider adding one to your garden. We feed our red crawlers non-protein kitchen scraps, torn newspaper, shredded mail and water to get gallons of this black gold every year. Worm manure is sold as worm castings in stores. Learn how to vermicompost - http://www.umass.edu/umext/jgerber/wormpowerpaper.htm
Epsom salts are another old-fashioned bloom promoter that adds magnesium to the soil. Not everyone supports their value - http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/Epsom%20salts.pdf
Fish emulsion, fish meal, kelp and seaweed are often sold in combination. Fish byproducts provide 5% nitrogen, 2% phosphorus and 2% potassium. Most organic greenhouses use it as a foliar spray at half the recommended strength. Seaweed provides valuable micronutrients.
Green manure is a crop you plant in the fall and dig under in the spring. Most of the recommended ones pull nitrogen from the air over the winter and literally plant the nitrogen into your garden soil. It's amazing. Seeds include hairy vetch (I do not like hairy vetch!), crimson or white clover, cow peas, fava beans, winter rye (rye is allelopathic and retards seed germination), rape, oats, winter wheat, etc. Hemp, sorghum and rye can help prevent destructive nematodes - http://edis.ifas.ufl.edu/vh037
Gypsum is an inexpensive calcium and sulphur source that is applied every 3 years. It may be unnecessary though - http://www.uwex.edu/ces/crops/Gypsum11.htm
Mycorrhizae are those beneficial fungi that everyone is talking about. They make your plants healthy. Buy them or make your own worm and leaf compost to get them free.
Rock powders - Ground phosphate rock, granite dust and greensand are considered organic necessities. Apply 8 pounds per 100 square feet every 5 years. The jury is still out on rock powders - http://www.pmac.net/rockdust.htm
Wood chips grow Basidiomycetes fungi that turn the wood into humus and most gardens benefit from more humus. OK to apply yearly.
Wood ashes from wood burning fire places that are not chemically treated will create an alkaline soil loaded with calcium, potassium, phosphorous and magnesium. Avoid putting around holly, yew, azalea, potatoes, blueberries and other acid-loving plants. http://www.hort.purdue.edu/ext/woodash.html
Compost piles provide an uncomplicated, free way to feed your soil. You can just pile up all your fall garden trimmings, grass clippings and leaves and cover them with a tarp anchored by rocks or cinder blocks. Or, you can build a structure of cinder blocks, cattle fencing, wood pallets (you see the broken ones with free signs on them everywhere!). Put the pile or structure under a tree or near a fence for shade and close to a water source in case it just sits there and you decide to water it to speed up the process.