Just returned from Montana on Aug 16th. Absolutely beautiful! Glasier National Park is a definit "Must See" Fly into Kalispel and rent a convertible for 2 days. Drive the "Going to the Sun" Road. Stay the night at Many Glasier Lodge for the night and drive back the next day. Make sure you switch drivers, scenery is too gorgeous to spend the time driving the whole time. The view is like being in your plane - your at altitude! The road closes at the end of September and re-opens sometime in May I believe.
www.sporty.com has a Western US Pilot's Guide. I heard it was a good book - Covers Arizona, California, Colorado, Idaho, Oregon, Montana, Nevada, New Mexico, Utah, Washington State and Wyoming. Has descriptions of things to do in the area, accommodations, and airport pictures with helpful information, ie frequencies, hazards, services etc.
I believe there is a special Sectional from the FAA for the Grand Canyon. Check out their website to order.
www.faa.gov
Also, if your going in the June, July and August time frame, you will need to dress in layers! The temperature difference in the morning, afternoon and evening is often 30 or 40 degrees. Not unusual to have an 80 degree afternoon and a 45 degree evening and the next morning wake up to 35 degrees. Bring Binoculars, and buy Bear Repellent!
Check out the book "1000 places to see before you Die", it covers some great areas of the western US. You are going to have a blast!