First rule is that I never do more than 45 minutes on the trainer, maybe a bit more with a warm up. If I'm doing 45 minutes, then usually I'm doing one of the rides from the Graeme Street Winter Training for cyclists. It's not on a DVD, except for one very difficult intervals and yoga workout, it's just in a book. I keep very focused on what I'm supposed to do next, looking at the very big clock with a second hand that I bought to keep track of each section of the rides. I also put on the radio very loud. Even though the bpm of the songs doesn't always match the cadence of my ride, it does keep me going.
Sometimes I get on the trainer for 20-30 minutes of an easy spin to warm up before a core work out or yoga. I watch TV during these rides or again, put the radio on. Once in awhile my husband and I are on the trainers at the same time, so we talk.
I mix this up with spin classes at the gym, but not so much this year and winter sports. I also ride my hybrid bike outside on the road whenever the temperature gets above 35. These are short rides, sometimes just 7-8 miles, not more than 20, but on a heavy bike, I get a good workout.