Cedarbrook Campground in Lebanon is open year 'round. It's a nice campground.
Winton Woods is excellent but not open in the off season. Can be hard to get in, too, so advanced reservations are a must.
Winton Woods - Great Parks of Hamilton County
Little Farm On The River is another good campground but kind of far from downtown Cinci, it's located in Rising Sun, IN and is open all year. Get a river front site for sure in the lower section.
Little Farm RV Resort
East Fork SP is good, too.