I'm over in Ohio, but usually make it to Indiana a few times a year for either a day trip (to the little state park at Liberty), or for a long weekend at Brown County or Midwest.
Indiana takes much better care of its trails than Ohio, so it's worth the trip and the small park use fee.
I like Brown County - plenty of good riding there, nice variety of trails with plenty of options. And I like being able to do rides as a loop, instead of always coming in and out of camp on the same trail.
The campground is also nice and nicely-kept, so it makes a good "test ride" for our first camping trip each spring.
I've heard Deam Lake is nice, but we've not been there yet. Might shoot for there, or Harrison-Crawford in the coming year.