My wife and I will be driving cross-country in a couple weeks, and will be looking for camping spots as we go. Here's some idea of our plans:

Nebraska - we'll be on I-80, and it looks like there are a number of state parks near the interstate. Something toward the east side is what we are looking for, as we'll start that day in Laramie, WY. Just a nice place to camp is all that I'm hoping for.

Missouri - we'd like to do a bit of biking on the Katy Trail, so looking for something that is near the trail or has immediate access to it.

Illinois/Kentucky - anything nice is OK. Access to, or proximity to, a car-free trail for bicycling would be a definite plus. We'd prefer to stay somewhat south in Illinois.