Hooked on Driving has three events at Autobahn Country Club this year.
I would also check out your local SCCA and/or NASA club(s). They often host open track days. Check the regional sections of all the different forums online, there are a lot of events organized this way.
I have also found that if you hang around the larger car shows you can find some "grassroots" sports car clubs that rent tracks. The trick is to talk to the owners of cars more likely to do open track racing (think Miata, BMW, FRS/BRZ, and the like) since the vast majority of Mustang/Camaro/<insert muscle car here> owners are only interested in drag racing.