I have to agree with Vermithrax, the Death Star doesn't exactly fly like a bat out of hell. More like that old guy in the fast lane driving 35 mph. with his turn signal on. You can't just make a jump to lightspeed in that thing and expect to travel from system to system destroying planets in a drunken joyride. There had to be plans for several to be built and deployed across the galaxy.
I did some searching and found this at theforce.net/swtc/ds/index.html:
At least one prototype Death Star was constructed at the secret weapons research facility within the perilous Maw black hole cluster near the Kessel system. Consisting of little more than an exposed frame with reactors, superlaser and propulsion systems, this prototype Death Star was never intended for active or sustained deployment. Facing attack by a New Republic task force seven years after the Battle of Endor, the staff of the Maw facility took the prototype and fled into the outside galaxy, with disasterous results. [Jedi Academy Trilogy]
Incomplete twin Death Stars were under construction in orbit around Imperial Centre at approximately the time of the Battle of Endor. Unfortuantely, it seems as if neither was ever completed far enough to be useful. It is unknown whether the Rebel Alliance was aware of the existence of these nascent battle stations when the attack on the Endor facility was planned. The rebels probably would not have had the audacity to assault the heavily fortifed Coruscant shipyards, even if they knew about these ominous constructions. As bait, these stations would be useless to the Emperor, and he would find little value in allowing the existence of these stations to be leaked to rebel spies, as he did for the Endor project. In any case they seem to have been abandoned and dismantled within months of the Emperor's fall. [The Illustrated STAR WARS Universe]
Darksabre: This vessel was a Death Star stripped down to its fundamentals: the main reactor and superlaser shaft. Its construction was commissioned eight years after the Battle of Endor by Durga the Hutt, who retained the services of the chief designer of the original Death Star, engineering genius Bevel Lemelisk [SW Tales #4, Darksaber]. Lemelisk had serious doubts about the quality of workmanship exhibited by the Hutt's construction crew. He escaped scant seconds before the destruction of his latest brain-child, and was taken into the custody of the New Republic. [Darksabre]