Churchill River
The Churchill River is not so much a river as a system of lakes, rivers and falls, all flowing in approximately the same direction. This maze of waterways is part of what makes it one of the best canoeing destinations in Canada. If you like whitewater canoeing, you can have it in abundance, or you can portage around whitewater. Otter Rapids is right below the launch point on Devil Lake, and it is a pretty nice, long class 3. Surf City, above Barker Lake, is a small safe class 3 that is great for playing in.
Access
The highway up to La Ronge is great, but north of La Ronge it gets a little sketchy, then turns to gravel. After you cross the bridge over Otter Rapids, keep going for 5 or 10 minutes before turning off to the launching point on the left. You launch into Devil Lake. A great destination from here is Barker Lake, which takes one portage (around Mosquito Rapids) and only a few hours. There are lots of campgrounds on Barker Island.
If you want to go south / east, launch from the campground right after the Otter Rapids Bridge.