Saruman

Saruman is a Canon Character in The Lord of the Rings. He is also called Curumo (in Valinor), Curunir, and Sharkû/Sharkey. He is a Maia who was the leader of the Istari or Wizards, a group of Maiar sent to Middle-earth in the form of old men to guide its inhabitants in the fight against Sauron. He was known both for his skill with machinery -- which the meaning of his name, man of skill, reflects -- and his melodious voice. He was extremely good at persuading people. During his stay in Middle-earth, he initially travelled around (particularly to the East), but for the last three hundred or so years of the Third Age he lived in the tower Orthanc, in Isengard.

Role in The Lord of the Rings
Warning: Spoilers for the plot follow.

Saruman had extensively studied the Rings of Power. He also took possession of a palantir in Orthanc, which allowed him to see far distances in space and time. Gandalf speculated that at some point he looked toward Mordor and was caught by Sauron. Saruman decided to turn traitor and pretend to work for Sauron. He sent Radagast, another Wizard, to tell Gandalf to come to him for counsel. When Gandalf arrived, he tried to convince Gandalf to join him; when Gandalf refused, he imprisoned him at the top of Orthanc. After Gandalf escaped, he openly showed his "allegiance" with Sauron. At the same time, he sent his Orcs out to seek for the Ringbearer, so he could have the Ring for himself, and also to attack Rohan. His servant, Gríma Wormtongue, drove both Théoden, the king of Rohan, and his niece Éowyn to despair. Unfortunately for him, Gandalf healed Théoden and the Orcs cut down trees in Fangorn, which angered the Ents who protected the trees there. The Ents attacked and destroyed Orthanc. When Gandalf and Théoden arrived, he attempted to persuade first Théoden and then Gandalf to make peace with him; both refused. Gandalf broke Saruman's staff, leaving him almost powerless, but Saruman was still able to convince the Ents to let him go free with Gríma Wormtongue.

After a chance encounter with the triumphant good guys, Saruman headed for the Shire. Through a cousin of Frodo's, whom he later had Gríma kill, he had managed to take over the Shire while Frodo, Sam, Merry, and Pippin were gone. His servants had chopped down trees, destroyed buildings, caused general mayhem, and instituted a tyrannical (especially by Hobbit standards) set of rules, and imprisoned any who opposed them. However, his plans were again foiled when Sam, Merry, and Pippin led the Hobbits in an uprising against him. He was still able to "welcome" Frodo home to Bag End. He was able to convince the Hobbits, except for Frodo, that killing him would leave the Shire cursed, but Gríma, sick of following him, cut his throat.