Chutes Provincial Park is our favourite park to stop when we're traveling between Sudbury/Manitoulin Island/Sault Ste Marie. The park is right off the Trans Canada Highway and has some AMAZING waterfalls!
Although it's not a big park, it's 100% worth seeing - even if you just stop to stretch your legs and hike the Twin Bridges Trail along the cascading Aux Sables River.
We would suggest 1-2 nights to see the whole park (there is one trail and a beach for swimming). Chutes is also used as a home base for people visiting Manitoulin Island and nearby hikes/parks.