I just discovered this site a few hours ago and I have to admit I really wish I had stumbled upon it earlier. So much good advice here; I decided to post myself asking for input from all of the helpful members.
Not wishing to bore with unnecessary details, I am heading out to California with my fiancee to deal with some family matters, and we decided to turn it into a road trip. We have the general route planned out, made three budgets (the ideal budget, the likely budget, and the "everything went wrong" budget. The plan is to do a combination of car camping, budget motels, and we have several places to stay for free along the way (always nice to have friends scattered about the country). Seven to ten days will need to be spent in northern CA... the rest of the trip is at our discretion for the most part.
Details: 50 days. Start in Madison, WI, end in Iowa City, IA. The rough route: Madison -> Minneapolis, MN -> Rapid City, SD -> Bozeman, MT -> Seattle, WA -> Portland, OR -> Northern CA (the necessary part of the trip) -> Southern CA -> Vegas -> Flagstaff, AZ -> Santa Fe, NM -> Denver, CO -> Omaha, NE -> Iowa City, IA
California is somewhat glossed over because I have spent much time there and we do not plan on doing much sightseeing there this trip.
Realizing that we do not have enough time to do a fraction of the things we would like to with unlimited time and money, I am asking for advice on MUST SEE things/places on the route. Things that regardless of the time constraints would be almost criminal to miss. A few spots on our radar are The Badlands/Black Hills/Rushmore, Glacier Nat'l Park, Yellowstone, Grand Canyon, White Sands... the well known tourist spots. Having never spent much time anywhere along this route though, I am sure many members of this forum have wonderful suggestions of other well known or even out-of-the-way gems. Any suggestions on sights, places anyone recommends for camping, eating, unique side trips (like the world's largest ball of twine), etc. would be most appreciated.
Looking forward to lots of driving... :)