(almost) every fall when the leaves change their colors, I make the drive up to the Muskoka area, where there are excellent 2-lane winding blacktops. For example, you could take:
* 400 North
* take 11 past Orillia
* after Huntsville, take 60 East - this is the beginning of the interesting scenery and roads
* take 35 - this is the best part, and will eventually merge with 115 and the 401 at around the Newcastle area
Not the place for outright top speed runs, but the winding roads make the drive interesting. And because there are always those slower cars, you will want to test the midrange-to-highend power of your car (better if it is one of those inline-sixes or 16-valvers), when you overtake them. This will also allow you to practice overtaking, which is an important skill on 2-lane roads.
Drive safely though, and give yourself (and other drivers) a lot of margin. My car does not have daytime-running-lights, so I turn on my foglamps, so I will be more visible to oncoming cars and those I overtake (important on winding roads, where other drivers do not see you early enough, compared with long straights).
The winding roads also give you an opportunity to appreciate the high-speed ride and handling of your car. Also, I haven't seen a cop car anywhere there - the winding 2-lane roads are more difficult to monitor because there are less opportunities to get a "fix" on a car's speed (I hope I'm not speaking too soon).
Or, you can take in the scenery with someone special riding shotgun. Or if you are into nature photography, there are many picturesque views (you have to time your visit to have the leaves still on the trees, for maximum effect). Or you can sample the many Bed-and-Breakfasts along the way.