The Oracle

Odin is a God that has many many names. He was as Wodan/Wotan/Woden to the Saxons, and Odin to the Norse. He has been called the Alfoder (Allfather, or Father of All) and Hanga (God of the hanged). Another of Odins names is Ygg. The Norse name for the World Tree (or World Ash) is Yggdrasill, which means 'Odins Horse'.
Not only is Odin a God of many names, but also of many things. In my research i have come across him listed as a God of the sky and war (traits he inherited from his predecessor), death, victory, music, poetry, prophesy, wisdom, healing, magic and as a shape-changer. A busy God indeed!
He is known as the son of Bestla and Bor. He had several wives and many children.
With Frigg, his first wife he had Baldur, Hod and Hermod. With Jord (an Earth Goddess) he had Thor. With the Giantess Grid he had Vidar, and with Rinda he had Vali.

He is referred to as the King or Chief of the Gods, but this wasn't always the case. The original Chief was Tyr, a God of battle and the Lawgiver of the Gods. At some point in Germanic history, Odin supplanted Tyr as the leader of the Aesir (one of the two main races of Norse Gods, the other being the Vanir).

As the title 'Allfather' suggests, Odin is credited with creating not only the Earth but also Humans.
After Odin and his brothers (Vili and Ve) had slain the Ancient Giant, Ymir, they created the Earth with his body:
Ymirs flesh became the earth,
his bones and teeth became ricks and stones.
Rivers and lakes were created from his blood.
The sky from Ymir's skull, secured at the four corners by dwarfs called North, East, South and West.
Ymir's brain became the clouds.
And from Ymir's eyebrows Midgard was created.

After the creation of all that is on Earth, Odin and his brothers found two logs. Odin gave them life and breath, Vili gave them brains and emotions, and Ve gave them hearing and sight. And so the first man, Ask, and the first woman, Embla came into being. Scandanavian and Germanic Kings of old claimed lineage from Ask and Embla and thus from Odin himself, making them, in part Divine.

One of Odins pursuits has always been the quest for knowledge and wisdom. He is most often depicted as having only one eye because he gave his eye in return for a drink from Mimir's Well of Wisdom. This taste of wisdom only made him want more, so he hung himself from Yggdrasill, impaled by his own spear for nine days and nights. During this time he symbolically died and was reborn. It was during this act of self-sacrifice that Odin created the Runic Alphabet. His personal Rune is 'Ansuz', although other sources say it is 'Othala'. Either way, both are powerful.
It is said that Human sacrifices were made to Odin. The obvious method for this was hanging from a tree and impaling with a spear. Some Sagas tell of at least two Kings (Kind Domalde and Kind Olof Tratalja) that were sacrificed to Odin in this way after many years of famine.
Another of his quests for wisdom involved him working as a farmhand for a Summer for Baugi.

Odin is credietd with bringing a magical mead of poetry to Asgard. Once it was stolen by a Giant who made his daughter guard it in a cave. Odin burrowed into the cave in the form of a snake. He changed back to his 'human' form and seduced the Giants daughter for three days. He then sucked up all the mead and held it in his mouth. Assuming the form of an eagle he flew back to Asgard where he spat it out into a pot, so all the Gods could enjoy it.

Odin had several animals attributed to him. He had two Ravens, Huginn (thought) and Muninn (memory) who flew over Midgard and reported back to Odin what was happening. He also had two wolves, Geri and Freki, and an eight legged horse named Sleipnir.
Amoung his magical artifacts were Gungir, a dwarven spear that never missed its target, and Draupnir, a magical ring. One of Odins symbols is the Valknut, three interconnected triangles.

Odin had three residences in Asgard. The first is Gladsheim, a hall where he presided over the Diar (judges) who regulated affairs in Asgard.
Then there is Valaskialf. A hall that housed Odins throne, Hlidskialf, from which he could see what whas happening in all nine worlds.
And the last, Valhalla. The hall with 540 gates where he entertained the Einherjar (the souls of great warriors slain in battle) bought to him by his Valkyries.

Several times in my research I have found passages stating that Odin will be killed on the day of the final battle (Ragnarok). It is said that the wolf Fenrir will be the one doing the killing. Why this is I haven't found out yet and none of the sites mentioning Odins impending death have given reasons or explanations.

The Romans equated Odin with their God Mercury. But Odin has also been compared with Lugus. Both are intellectual, have ravens and spears attributed and both are skilled at magic and poetry.

As an easily approachable God (by those who know him), he has been worshipped from Proto-Germanic Paganism right through to the modern day. Today he is worshipped, along with other germanic deities in Asatru ('faith in the Aesir').
There is a theory that Odin is based on a real Chieftain. For a very interesting read about this, I recommend 'Was Odin A Genuine Human Being' by Wilmer Thomas.
His influence can even be seen in in name of a day - Wednesday, or to the Norse, Wodensdaeg (Wodens Day).

Sources -
http://www.pantheon.org/articles/o/odin.html

http://www.thorshof.org/zodin.htm

http://www.timelessmyths.com/norse/teutonic.html

http://odin.org/gods.html

http://en.wikipedia.org/wiki/Odin

http://www.wizardrealm.com/norse/gods.html