I like Bannack as a well-restored frontier era territorial capital. Lemhi Pass is reasonably close by and it's striking to approach it from the MT side as Lewis & Clark did--and to see what they saw when they first peered over into Idaho in September 1805. Twin Lakes CG over on the western margin of the Big Hole is as nice of a spot as you'll find anywhere. Elevation about 7,500 means cool weather even in July/August. I like anywhere in the Big Hole and the adjacent Pioneer Mountains--lower and forested on the west side, higher and glaciated with tons of alpine features on the east side. I'd rate a cruise through along the Big Sheep Creek Backcountry Byway as top notch and next time I'm out there with camping gear I'm going to Morrison Lake down that way. The Centennial Valley between Monida and Henry's Lake, ID is practically deserted and has the true "Big Sky Country" look. We're actually headed out there soon and will be making our first traverse of the Gravelly Range, where 30 or so miles of graded gravel road holds elevations of 9,000' or more. Really looking forward to that.
We always partake of the baked goods at the bakery/cafe/coffee shop at the junction of I-90 and US 287 known regionally as "Wheat, Montana". Down in Dillon is a fine Mexican place known as the Dillon Taco Bus due to the kitchen and primary serving area being within a large flatnose bus. In Missoula, a late night breakfast at The Oxford is always a people-watching extravaganza with good vittles as a bonus.
Have a good trip!
Foy