20 to Orange. From there follow Rtes. 15 and 231 to Gordonsville and Charlottesville, where you pick up I-64 west to Lexington. All the Jackson-related sites are within walking distance, so you can leave your car at the visitor center. After paying respects at the graveyard where Stonewall and his family are buried, any Jackson fan should visit the campus of the Virginia Military Institute, where he taught before the war.
Admission is free.