Club Island is south of Manatoulin by about 2 or 3 miles and about half way across the south side of Manatoulin and has a good protected harbor. Good anchorage.
Rattlesnake island is also reported to have a good anchorage but a bit shallow. It is much closer to Tobermory.
Haywood island is near the east end of Manatoulin and has excellent anchorages.
All 3 are uninhabited.
I don't think there's much on the actual south side of Manatoulin.