I'm a little far (Cincinnati), but we usually get to Brown County a couple of times each year for a long weekend. That's become our "test drive" camping trip for the year.
I liked Midwest Trail Ride as well, other than having to ride that same stretch of trail to get between camp and the main trail system.
I've heard Deam Lake is really beautiful and we had plans to go there this year but had to call off at the last minute.
Maybe this coming spring.
I like the loop at Brookville Lake (near Liberty) - it's not long, maybe just eight miles or so - but we generally make a day ride out of it. Get there in the morning, ride the loop in one direction and go back to the trailer for lunch. Then we ride the loop again, this time in the opposite direction, and call it a day.
It's a very easy ride, and Indiana takes great care of it's horse trails so you don't have to deal with the vast expanses of mud that we do here in southwestern Ohio. Having said that, though I recently heard that Caesar Creek just did some major improvements to its trail system, and there's also Hueston Woods State Park.
Farther east, there's East Fork State Mudho. . .er, Park.
Also, Shawnee State Park has good trail (but primitive camping, unless you stay at Ben's Happy Trails); Paint Creek State Park is nice, we were just there on Sunday. And there's also Pike Lake, which I haven't ridden in a couple of years. From what I've been told it used to be pretty rough, but the last time I was there it didn't seem too bad. Rocky in parts, but some really nice riding as well.
One of the "jewels" of Ohio is Hocking Hills State Park, which would be quite a trek for you if you're in Indiana (think long-weekend), but it's really a beautiful area. Similar to Shawnee National Forest in southern Illinois, but more compact - lots of caves and box canyons, waterfalls, cliffs and boulders with huge trees growing on top of them. The state doesn't offer much in the way of horse camping there, but from what I've been told there are some nice private cabins that also have barns/paddocks for your horses so you can stay and ride.
I don't know many places in northern Kentucky to ride - the only one I've done was AJ Jolly, but there's not a lot of trail there to make it worth the trip from where you are. However, if you have any suggestions (within an hour or two of Cincinnati), I'm open to hearing them. It's always fun to check out places I haven't been before!