My best solution is some extra mileage on the bike, all well and good but it's bloody freezing at the moment and the conditions are a little dodgy to say the least. My mileage is going to be up on December's (I believe) but they'll be no real major rides this month. I'm back on the Push-ups programme and I've just joined a similar sit ups programme too.
A lot of people join gyms at this time of year, I'm not keen on the places and think you can achieve the same (or even better) results at home.
You can follow my fitness progress at Dailymile.com.