Late summer into October: WA SR 542, the Mt. Baker Highway. It's not a through road, so go to the end and then head back. As soon as you leave Bellingham the rural farm country is nice with views of Mt. Baker and the Twin Sisters from time to time. A bit farther along you begin to follow the N. Fork of the Nooksack River and things get more and more rural until you hit Glacier. After Glacier you are now in Forest Service land and there is no more development of any kind until you pass a highway dept. garage, the speed limit slows to 35, and you begin the real climb up a narrow winding road. Beautiful forest views finally give out to stunning alpine ones. Head all the way to the end past the ski area to "Artist Point" the name of which will make itself obvious when you get there. There are trails and views all over the place, your eyes will hurt from the beauty. (Go early, parking can be an issue later in the day.)
Winter: Same as above, but it stops at the ski area. Go skiing and most of the views mentioned above for Artist Point will be available to you, and you'll be able to ski too.
A few of good stops along the way:
Nooksack Falls. Past Glacier. There are signs for the turnoff, but not many. A narrow gorge and a big waterfall.
Milepost 44: Just west of mp44 are two turnouts (small, dirt, and not marked, plowed in winter). Park in the western one and follow the little trail there into the forest a couple of hundred feet to a HUGE western red cedar and some other similar giant trees. This is real PNW old growth rain forest and you'll be deep in the forest but right next to the highway.
Welcome bridge and bald eagles, usually in January: Between Deming and Kendall is a little store called the Welcome Store right at the turnoff to Mosquito Lake Rd. Go down Mosquito Lake Rd. a short distance to a bridge across the Nooksack River. Stop somewhere along here by the river and get your camera out. When the salmon are running there are flocks of bald eagles sitting in the trees, lining the river bank, and feasting on dead salmon. An amazing sight on the right day.