Red Mountain pass out of Ouray, Colorado. Drops down into the mountain mining town of Silverton, then back up over Molas Pass and down into Durango. Gorgeous drive. Must do it on a motorcycle some day. The "Million Dollar Highway".
Did that one last summer. I actually thought it was less scary than Highway 1, after hearing many people warn me about it beforehand. Wouldn't want to do it on an icy winter day, though. :)