Another vote for Blanchard Springs Caverns. Been to quite a few of the more famous caves (I'm a geologist) and this one is near the top of my list.
I wouldn't necessarily rule out Eureka Springs. Interesting place to at least spend an afternoon. A good selection of interesting restaurants.
Interesting camping around Lake Ouachita. Incredibly clear water.
While art museums aren't usually my thing, I was very impressed with Crystal Bridges near Bentonville. The price is right at free. I'd go back.
I'm guessing you've been to Gettysburg considering where you live. Pea Ridge is an interesting Civil War Battlefield in NW Arkansas that can take a couple of hours or all day, depending on how deeply you delve into it. One of the important battlefields on the western front.
I've been to or passed by Hot Springs NP a few times and just can't get very excited about it.
