For me working eve shift makes a BIG difference in the winter! Just getting to see daylight on working days helps a lot. Before my knees got hinkey I used to skate and cross country ski, activities which actually got me to work up a sweat. I still work out and anything physical helps a lot. Also I save new recipes to try, new books I've wanted to read, DVD's I've wanted to watch and a jigsaw puzzle or two for winter. I make an extra effort to get together with friends or have them over.
This gets me about 2/3 of the way through winter-after that I either hibernate or want to scream! (One of these years I'm gonna go south for Spring Training!)