Well developers closed the track in Jax. Closest one is in Gainsville.
Gainesville Raceway: Locator Map and Driving Directions
About 1-2 hour drive away. If you go there DO NOT SPEED through Waldo. Cops there set up a speed trap where the speed drops from 65 to 45, and they will write you up for 46.
Not much to do that I know of right now Truck related (I am deployed right now, and not up on what is going on now.)
However Doytona is also about a 2 hour drive down I-95. You could go dtrive on the beach, or visit Daytona USA.
Stop and see St Augustine. Lost to see around there.
Or if you want to drive on the beach near Jax you could go to Huguenot Memoral Park
Map of Batten Island, FL by MapQuest
This will get you near there.
And I know that there is a Mudhole in Middleburg just south of the city. Take I-295 to Blanding Blvd, go south on Blanding for about 10 - 12 miles till you get to CR 218, turn right go about 3 - 4 miles and it will be on the right. Not exactly sure where as it has been a few years since I been there. I am fairley sure that they are only out there on Sundays. Just not sure of the details.