Share 'What do you use for a Crop Cover/ Green Manure'

Just wondering what different members use for a crop cover, if you use one at all. I was thinking of planting some sort of winter rye where my garden is going next spring. I know that Abrizzi Rye which I plan to use has an estensive root system which will prep the soil for next spring as well as add to the organic matter of the soil. Also I was thinking of using alfalfa in the area where my gar...