Jackson not dying at Chancellorsville could have many different effects. One possible twist is vaguely similar to what takes place in the Newt Gingrich alternate history. Assuming that the fight at Gettysburg takes place as the first day occurred, leading up to the Union retreat through town to the heights, Jackson's attack may not succeed. An entire Union division, minus a reserve brigade, had entrenched on Cemetery and Culp's Hill since early afternoon, and there are few good staging positions from town to strike at that spot. Jackson's repulse might jolt Lee out of his determination to win at Gettysburg, but I don't believe that Lee can win a major victory against Meade in Pennsylvania.
As a military engineer and a native Pennsylvanian, Meade operated on very sound military lines, and had contingencies plans established from the moment he arrived in Gettysburg (Sickles would later use this against him). In all likelihood, Lee's lack of ammunition would probably force him to withdraw southwards to Virginia, especially if Meade falls back to the eminently sensible Pipe Creek line.
What, then, would be the effects of an invasion of the North that has no major battle? Would this be a moral victory for the South or the North, or would it have any effect?