Even if you've never been the type to go to the gym for a workout, Winter is as good a time as any to get some physical exercise started. Instead of hibernating and storing up fat from the delicious yet calorie-laden holiday feasts, choose to get in shape! On top of giving you more energy, improving your health and making you feel better in general, once the warmer weather comes again you'll also have a great new body to show off.
Gym memberships can be expensive, but the good news is that you don't necessarily need all that fancy and pricey equipment to get the job done. Some common games you might already have that will get your heart rate up are DDR and Wii Fit. These can both be great to play together. If that's not your thing, just start walking. If you don't like being out in the cold, walk briskly through the mall.
At-home workouts could include push-ups, crunches, jogging in place, weight-lifting (doesn't have to be your typical dumbbell... just pick up anything with some noticeable weight and have at it!), walking/running up and down the steps (if you don't have stairs inside your house, you probably have some outside; just please make sure they are not icy) and yoga, to name a few. Most libraries have a lot of work-out DVDs ranging from belly-dancing lessons and martial arts training to random aerobic exercises... these can be a lot of fun to try out as well.