i live in yonkers so there isnt that much over there but up the taconic parkway passed mahopac it becomes 2 lanes and awesome!
The Taconic is great to drive on.
The National Scenic Byways Program already compiled what is probably the definitive list of great American driving roads:
http://www.byways.org/explore/byways/
Most of these look fairly incredible.
Three personal favorite driving roads (that I've actually driven more than once):
1. Panoramic Highway or Shoreline Highway from Mill Valley, CA to Stinson Beach. Redwoods, sharp corners and finally ocean. Incredible. Only minutes (without traffic) from downtown SF but there's shockingly little traffic. Also, Stinson Beach is just cool. Marin County is criss-crossed with fabulous driving roads.
2. Vermont Rt 108 over Mt Mansfield in Stowe via Smuggler's Notch. Absolutely gorgeous countryside gives way to a switchbacks up to a genuinely eerie mountain pass. Blasting downhill you emerge into the alpine fantasy of Stowe and enjoy some delicious Ben+ Jerry's. Actually, there's too many great Vermont driving roads to list here. It's a little known fact that Vermont = driving heaven. Great scenery, well maintained roads, lots of curves, great roadside food, no traffic, high speed limits and extremely cool cops.
3. San Juan Skyway from Ouray to Durango CO via Silverton. They don't call it the Million Dollar Highway for nothing. This is the old west meets the Alps. Incredible Rocky Mountain views, abandoned mining ghost towns, desert etc. It's got everything. There's a little bit of traffic in the summer, so do it in the fall. For more fun, keep going until you hit Mesa Verde.