Well... here is a time line of Star Wars books.
Just as a starting point, I would recommend you start with Truce at Bakura as it picks up exactly where RotJ ends and then read forward on the list.
And skip the Young Adult books (the ones highlighted in that orangish redish color).
Keep in mind, they were not written in order so some facts in one book were not totally set in stone when another was written.
And then once you're up to date, then you can go back and read the prequel ones.
[Edited by Dhampy, 3/4/2010 9:01:50 AM]