I've found that CAA/AAA's triptick is extrememly helpful, and free. Plus, you can now get it online. I went to one of the offices and a woman there actually helped me plan my trip, including safe truckstops along the way, and helped me avoid any tolls. You just have to be a member, which is always a good idea if you're going on a roadtrip.
Get The Real Thing!
AAA.com's online triptik does well in a pinch, but keep in mind that it is nothing more than a Mapquest product with a few tweaks and alterations. AAA members can still obtain the traditional hand-drawn triptiks (for free, of course) at their local AAA offices.