Not particularly spell related, but still undead-happy:
Boats.  Yah, yeah, most undead are too stupid to really sail a ship.  So screw sails, row that puppy!  Skeletons and zombies are bright enough to follow drum instructions and a warship with three decks of rowers that never tire make *excellent* time.  
mining.  Again, not so good at the knowing when to stop digging before causing a cave in.  *BUT* they work tireless at simple pumps (archimedes' screw) to keep mines dry, don't use air, and you can always have a half-dozen of them working a drill crank as an undead auger.  
Mounts.  Why does everyone forget the zombie and skeletal horses?  Sure, they're slow but load those puppies down!  You can save a ton of cash by not feeding draft animals and undead don't suffer exhaustion.  
Oh and a nice trick for pale masters is to act like a flesh golem.  Once you get the arm and the body armor it doesn't take a whole lot.  Have your apprentice take the role of the master and fade into the background.