I do mostly cross country, although I have some Alpine equipment, too. In Idaho most Nordic trails are pretty hilly anyway.
I'll mostly go to Bogus Basin Ski Area, which is the closest place to Boise, Idaho. The Nordic Center is about 1 km past the Alpine slopes, and on a weekend by the time you find a parking spot you're just about at the Nordic Center.
The Mountain West Club will probably do a few X-C skis on the Park 'n' Ski trails, Goldfork and Banner Ridge by Hwy 21 past Idaho City. There will probably be a few to Tamarack Resort by Cascade Lake near Donnelly, ID. The resort and Alpine slopes have blossomed into quite a big, expensive operation, but the Nordic trails are still pretty reasonable.
Speaking of reasonable, Brundage Mountain near McCall, ID is a very nice Alpine slope. Over 100 miles away, I don't go there very often. In the past prices have been reasonable, lift lines are not bad, and snow conditions are often excellent. Temperatures can run 10 to 20 degrees lower than at Bogus Basin.
Sun Valley, Idaho is world famous, and it's pretty there, but it's kind of expensive.