Lots of great roads. Like RevRob said Hwy 37 between Libby and Eureka is about 60 miles of curves on nicely paved asphalt hung above the reservoir, with little traffic. Hwy 200 east of Missoula up the blackfoot river is another favorite, as is the junction road between hwy 200 and hwy 12 at Avon (high mountain rangeland). There's an old auto museum/collection in Deer Lodge. SW MT in the Ennis/West Yellowstone area is excellent, as is the big hole valley in Jackson/Wisdom country. The main throughways like US hwy 93 Missoula to Kalispell can be nuts, but most side state roads are relatively lesser travelled. Everyone likes hwy 12 over Lolo Pass into Idaho (the famous "curves next 77 miles" road).
"Going to the Sun" road in Glacier park is worthwhile, lots of rv's, but it's still worth seeing.
If you're headed towards Victoria, the Nelson area in southern BC can't be missed.
I ran into two guys from Edmonton on a HD chrome-buying-spree while staying in Great Falls last July. I inquired to them about Nelson, they said "too many curves". I was stunned speechless.
jh
