Samwise Gamgee:

One of the four hobbits in the Company of the Ring, Sam was the servant of Frodo Baggins. He gained a sword in the Barrow Downs, and sneaked into the Council at Rivendell. He was included in the Company of the Ring. Sam followed Frodo when he left the Company at Parth Galen. The two of them gained Gollum as their guide from the Emyn Muil to the passes of Cirith Ungol. There Frodo was captured by orcs, though Sam managed to remove the Ring. He resisted the Ring and rescued Frodo, returning the Ring to him. Sam managed to keep Frodo going long enough to reach Mount Orodruin, where he helped Frodo from the Sammath Naur, after the destruction of the Ring. Thus it was that both were seen and rescued by the Eagles.

After the War of the Ring, Sam used the gift of Galadriel to restore the Shire, and married Rose Cotton. Sam accompanied Frodo to the Grey Havens, though he remained behind. Sam was elected the Mayor of the Shire seven times. It is believed in the Shire that after the death of his wife Rose, Sam went to the Grey Havens and from there into the West to be with Frodo and Bilbo.

Sméagol:

A hobbit who lived along the banks of the Anduin River. It was his friend Déagol who found the One Ring where it lay after Isildur's death. Sméagol murdered him and tool the Ring, calling it his Birthday Present. An undetermined amount of time afterwards, Sméagol was forced to leave his home, who called him Gollum.

During the Quest of Mount Doom, Frodo used the name Sméagol for the creature that Gollum had become.

Smaug:

The dragon who caused the abandonment of Erebor, Smaug was killed by Bard the Bowman. The secret of his weak spot was discovered by Bilbo Baggins, who was with the thirteen dwarves who had come to regain their treasure and kill the dragon. This quest was also supported by Gandalf, who believed that the dragon could cause a lot of trouble with Sauron. Smaug's body rests to this time in the Long Lake, amid the ruins of Lake Town. Though there were many jewels encrusting his body, nobody was courageous enough to dive to collect them.

Saruman:

Saurman the White was another of the Istari, and counted their leader. He was the most powerful and had a voice that was able to daunt and command anybody. His specialty was the Rings of Power. He settled in Orthanc with the permission of the Steward of Gondor, and there found one of the Palantir. He attempted to set up as a power of his own with orcs and a creation of his own, half-orcs. After his attempt on Rohan, Saruman was cast out of the Istari by Gandalf the White. In revenge, Saruman attempted to ruin the Shire. The hobbits, Frodo, Merry, Pippin, and Sam thwarted this desire, and Saruman was killed by his servant, Gríma Wormtongue.

A Maia, Sauron was the servant of Morgoth. Called in the First Age, Gorthaur, Sauron did not submit to be judged, at the end of the First Age. In the Second Age of the Sun, Sauron forged the Rings of Power with the aid of the Elven-Smiths of Eregion. At this time he could still take on a fair appearance, and fooled almost all other than Círdan, Gil-Galad and Elrond. At this time, Sauron secretly forged the One Ring with the words

When the Elven-Smiths realized this, they hid away the Rings that they had made. This caused war between Sauron and the elves. Sauron managed to recover all but the Three Rings of the Elves.

As Sauron's dominion over Midle-Earth grew, the Men of Númenor, who by this time had grown proud and domineering, sent a force so great as to send his own armies into hiding to Middle-Earth. Sauron surrendered, and was taken to Númenor as a hostage. There he gained power over Ar-Pharazôn, the King, and turned his mind fully against the Valar. He encouraged Ar-Pharazôn to break the Ban and attack Aman. In the resulting Change of the World and the destruction of Númenor, Sauron lost the ability to take any fair shape. He returned to Middle-Earth and took up the One Ring again. Soon after he made war on the Exiles of Númenor in both Arnor and Gondor. Thus came about the Last Alliance of Men and Elves. Sauron killed both Elendil and Gil-galad, but Isildur the son of Elendil, cut off the One Ring from Sauron's hand.

Sauron was destroyed for that time, but soon began to take shape in what was called Mirkwood after his coming. In the year of the Quest of Erebor, he was forced out, but ten years later, Sauron re-entered Mordor and began to search for the One Ring. Seventeen years later, he found where it had been, but the Ringbearer had fled the Shire. Sauron, after Aragorn wrested the Palantir from him, let forth war on Gondor and was distracted from searching for the One Ring. This was his downfall as Frodo, the Ringbearer, had slowly been making his way to Orodruin, Mount Doom, where on the very eve of Sauron's victory, he destroyed the One Ring by throwing it into the Cracks of Doom. Thus was Sauron destroyed for all time.

There are two different opinions on what form Sauron took in the Third Age. One, generally disregarded, which is supported by Frodo's description, based on what he saw in the Mirror, is the Lidless Eye. Other evidence for this form comes from his insignia. The other form is generally believed to be the correct one. This one is the form of a man. The evidence for this one comes from the words of Sméagol, who said that he only had nine fingers. Given that Sméagol saw him face to face, his words are the most definitive answer.

Salmar:

The maia who made Ulmo's horns.

Shelob:

Greatest of the giant spiders remaining in Middle-Earth, Shelob was said to be a daughter of Ungoliant: But none could rival her, Shelob the Great, last child of Ungoliant to trouble the unhappy world.(LOTR.750)

She lived in a pass over the mountains into Mordor, where rumor of her had spread, until the pass was named Cirith Ungol, the Spider Pass. Few had ever survived attempting it, save only Frodo, Sam and Gollum (who worshiped her). Frodo and Sam survived only because they had the Phial of Galadriel which kept her back while it was held up. It is suspected that Sam, fighting for both his own and Frodo's lives had mortally wounded Shelob. Certainly no more was ever told of her.

The Lord of the Rings
The Silmarillion
The Hobbit
The Complete Guide to Middle Earth by Robert Foster