1. Plan a Thanksgiving Day Event. Meet up with your friends, family and neighbors the morning of Thanksgiving and exercise together. You can start a tradition and play a game of football, baseball or any other sport. Good competition will always get you in the mood to work hard. You can also gather everyone up for a Thanksgiving Day run or walk around the neighborhood.
2. Run a 5k. There are lots of organizations that schedule 5k runs around Thanksgiving. They usually support a great cause and are also really good workouts. Running a 5k burns a huge amount of calories the day of the race in addition to all the training you do leading up to the big day.
3. Make a Deal. Thanksgiving is one of those times you can't always control yourself. You might think you'll only eat a little but once all those dishes come out of the kitchen, more food is going to wind up in your plate than you had hoped for. To negate some of those calories, make a deal with yourself (you can include friends and family too). Tell yourself that for every serving over what is normal, you'll run 1/2 a mile or 10 minutes. Get creative and make your own criteria but make sure you follow it. If you tell others about it, you're more likely to stick with it.
4. Pre/Post Thanksgiving Workout. Since Thanksgiving is all about tradition, think about how the Pilgrims and Indians got around back in those days. There were no cars or busses. If they wanted to get somewhere, they'd walk or ride a horse. Since it isn't realistic to walk (or ride your horse) to your Thanksgiving Dinner, simulate the walk by working out 30 minutes longer than normal on the Wednesday before Thanksgiving and 30 minutes longer on the Friday after.
5. Walk it Off. Don't forget to have a post Thanksgiving Meal walk. You'll probably be too heavy to run or do any other form of rigorous exercise. Walking will burn a few calories and let your mind unwind after being stuck inside all day long.