Update to my reply of almost two years ago:
Subscribe to ZWIFT for your Winter training.
The racing on Zwift is intense and the training programs and graphics will motivate you! You'll meet lots of othe fast old farts and some really fast young farts!
Sufferfest, Trainer Road, Golden Cheetah, Rouvy, Virtugo, Road Grand Tours all have their strong points and are also fantastic indoor training programs. Most have free trials so give them all a try.
I did 4,700 miles over last Winter on Zwift. It's probably the most popular of the computer based programs, but as stated above they all off something to every rider and racer. I came out swinging this Spring when I hit the road and the snow finally melted away, My conditioning actually declined a little when I stopped riding Zwift and moved back to 95%-98% road training / riding.
Ride On!