Christopher Lake: you must try out "The Yellow Fender". Fresh, homemade food with some imagination thrown in! Also, their desserts are worth the drive.
Prince Albert: I haven't been to the new Turkish place in the South Hill Mall, but I have it on authority that it's worth the drive. Try going during the day though, as I believe it's closed evenings.
Hafford (North of Saskatoon, West of Blaine Lake, easy to do a slight detour on the way to Big River): Go to the "Silver Sword and Chalice" with an appetite and a camera. The chef is amazing, has a ridiculously huge menu (try the fried chicken or the eggplant parmesan if it's in stock that day) and sit back and enjoy the comic collection, 8-tracks, and lots of records to listen to. It will be the highlight of your Saskatchewan trip. I guarantee it.
Big River: people are always oohing and ahhing about "3rd and Main" but I've never been there myself. Usually if we're near Big River we're camping, not eating out!
Good luck, and enjoy your travels.
VC in Regina
I also like the dim sum and other Chinese food at Genesis, which is more economical than Bliss or Truffles.
Also see this thread: http://chowhound.chow.com/topics/831089