E.T.
It depends on what kind of vacation you are looking for. These are some of my favorites:
Yellowstone/Grand Teton and Big Horn Mountains in Wyoming
Seattle
Myrtle Beach
Colorado Springs/Estes Park Colorado
Maui
Chicago
Banff, Canada (not in the US, but not really international travel)
San Diego
The Apostle Islands in northern Wisconsin
Kentucky-- a must stop is Horseshoe Bend Winery near Lexington (email me if you want contact information)
These are all places that I have been to multiple times or would love to go back to again!