One of the most recognizable aspects of Star Wars is the lightsaber. Whether its the image of the laser sword, or the familiar snap-hiss noise of its activation. The lightsaber is synonymous with Star Wars. While the original trilogy gave us Luke, Obi-Wan and Vader using what can best be described as standard lightsabers (note that Vader's hilt was over sized) .The Expanded Universe and the Prequel Trilogy gave us more variety in lightsaber design and technology, from the movies most notably, Darth Maul's Dual-bladed lightsaber, Count Dooku's curved hilt, and Master Yoda's minaturized (arguably Shoto length) saber.
The Double-Bladed Lightsaber also referred t as the Saberstaff, is an uncommon weapon for Jedi and Sith alike which gives both new advantages and disadvantages to the wielder. Most famous for its use was the Sith Lord Darth Maul, seen in Star Wars: Episode I: The Phantom Menace, as well as numerous comics and novels. More recently the double-bladed lightsaber has made a remergence in The Clone Wars TV series through a variant used by Sith Apprentice Asajj Ventress and the soon to be seen Sith Warrior Savage Opress. Savage Opress the brother of Darth Maul uses a lightsaber that may very well be his brother's old weapon or simply one modeled after it. Ventress on the other hand has two curved handled lightsabers that have the unique ability to join together to form a double-bladed lightsaber when she so desires. 
Later in the Old Republic Era we have the story of Darth Bane the originator of the Rule of Two and his apprentice and successor Darth Zannah who wields another modified version of the double-bladed lightsaber, this one with slightly shorter blades for increased speed and maneuverability making her movements shorter and quicker.
In Drew Karpyshyn's novel, Darth Bane: Path of Destruction, Bane receives training at the Sith Academy on Korriban, and learns from Sith Blade Master Kas'im, who wields a double-bladed lightsaber. Kas'im describes both the benefits and detriments of the weapon.
In combat, your mind tries to keep track of each blade separately, effectively doubling the number of possibilities. But the two blades are connected: by knowing the location of one, you are automatically aware of the location of the other. In actual practice, the double-bladed lightsaber is more limited than the traditional lightsaber. It can do more damage, but it is less precise. It requires longer, sweeping movements that don't transition well into a quick stab or thrust. Because the weapon is difficult to master, however, few among the Jedi-or even the Sith-understand it. They don't know how to attack or defend effectively against it. That gives those of us who use it an advantage over most of our opponents.
With the introduction of Savage Opress into the Clone Wars we are going to see more double-bladed lightsaber action then ever before. Just wait until you see the incredible duel between Savage, Obi-Wan, and Anakin. Flashbacks to Maul, Obi-Wan and Qui-Gon Jinn anyone?
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