I-70 in Colorado between Grand Junction and Denver - scenery like no other, on an interstate no less. I did this on the Katatonic back in 2000 - probably the best riding of that trip (rode to CA and back - all on interstates, visiting friends)
A navy Buddy recommended the Monterey Bay Aquarium, but, that was too far out of my way.
As long as you avoid NOT stopping for gas in death Valley (I met a sportster rider who did, not sure he could have made it anyway, then you'll be fine =)
-John =)