Charleston is a tiny town west of North Bend and Coos Bay. There isn't much to see in the town itself but west of town are a few things that make it well worth the trip out here (via the Cape Arago Highway).
Sunset Bay State Park - Beautiful beaches surrounded by sea cliffs, hiking trails to Shore Acres and Cape Arago State Parks, campground (online reservations), swimming, boat ramp and lots more. We didn't stop here, but it would have been a nice place to stay overnight.
Cape Arago Lighthouse - You can't get to the lighthouse itself, but you can see it from an overlook about a quarter mile south of the Sunset Bay Campground. See pictures below.
Shore Acres State Park - A definite must see! Gorgeous formal gardens, breathtaking scenic views, hiking trails connecting to the other two state parks. See pictures below.
Cape Arago State Park - The one road to this park (Cape Arago Highway) was closed at Shore Acres State Park in September 2014, so we couldn't visit it, but it sounds like a nice place. It has hiking trails connecting to the other two state parks, beach access, wildlife viewing and more.
Keep in mind that getting to any of the parks described above is an out and back trip from Charleston. The Cape Arago Highway ends at Cape Arago State Park, so you have to go back to Charleston before you can head south on Seven Devils Road and hook back up with Highway 101 South.