Take the Yellowhead through Saskatchewan. It's got some rolling hills and stuff. It's a much nicer drive in the winter...not much traffic except for you and the truckers. There's not much to see in that part of Saskatchewan this time of year though. There's the potash mine at Esterhazy, but they've limited access to it so you can't get your friends to give you rides in the buckets of the big loaders anymore.
If you were coming through in the summer I know a few little tourist attractions, like the Luthi House. They shut down in the winter though.
Mind you, if you stop in S'toon there's the Western Development Museum...that's cool. Then you can pound the 8-1/2 or 9 hours to Winnipeg. While here you should check out the Museum of Natural History and walk around the Exchange District a bit. The Exchange District is the part of town where they shoot the movies because it looks like 1920's Chicago. There's also The Forks, where the rivers come together. There's a really cool walking bridge there. Again, not much going on in the winter. You're coming just a little too late for Festival du Voyageur.
Give me a call when you're here, we'll grab a beer or something.
When you pull out of Winnipeg, plan on making Thunder Bay...that's another 8 or 9 hours. You won't see much but rocks and trees once you hit the Ontario border. At first you'll think it's pretty, but soon you'll realize that it's dead boring. You'll be tempted to speed. Don't. There are a lot of moose on that road, they come up to lick the salt in the winter, and if you hit one you will be killed. Also, the truckers are all insane, so be careful.
Definitely check out Kekkabekka falls when you are in Thunder Bay. It's very cool, especially if there's some ice on it. I used to stay in a hotel that was just south of town in Thunder Bay...nice quiet little place. It's a Best Western, but I can't remember the exact name.
Next time you come through, make it in the summer. There's a lot more going on.