A relatively unknown, but great ride, is the Auburn CA Century. Many options for distance. Tough climbs, especially out of the American River. Beautiful time of the year to do it. The only stretch you will really get traffic is the last leg from Foresthill to Auburn. The rest of the route is just beautiful backcountry roads. The 140 mile option is a tough ride, but it can be done if you have put in the hill training rides. I used the route (without the Robinson Flat out and back) many times while training for doubles
http://www.wildestride.com/