Note that I try to keep this info up-to-date, but be sure to check the web links, and also check with these parks & locations to be 100% sure (I could be wrong, and sometimes their rules change...)
Lake Harris is just south of Jordan Lake, and is the lake that Shearon Harris nuclear reactor is on. Car-top boat launching allowed (no trailer launching). The launch site is located near the peninsula trail head and picnic area. Their webpage is pretty detailed, and I don't see mention of a launch fee, so I'm guessing it's free(?) - A friend of mine who canoes there also said it's free.
(35.619236,-78.926854)
Google Satellite Map