If you want solitude, black water, limestone bluffs and sandbars, the Suwanee River is a great trip. There is an outfitter at Live Oak Florida who will run shuttle for you. I used to park at their place and get them to take me up to Fargo Georgia to put in. Depending on current and your paddling prowess, it takes five or six days to get back to the take-out where your vehicle is parked.
http://shop.suwanneeoutpost.com/

If the Suwanee is too high or low for good camping and paddling, they have alternate trips on other nearby rivers. Spring is a good time to go--less heat and bugs. I had some very good times there.