Jedi Apprentice was a great series. I had five volumes, and someone stole them. Blasted thieving people...
Shatterpoint is fantastic and far above most prequel-related stuff. The Thrawn Trilogy really captured the classic Star Wars feeling too, in my humble opinion.
I liked th first two Republic Commando volumes. Haven't bothered to read the rest, but it was an interesting diversion from Jedi, the Force and such.