There seems to be a lot of angry comments going around about The Hobbit being stretched into three films. People seemed to be focussed on the fact that the Hobbit is a much smaller book than The Lord of the Rings, (my copy being only 289 pages) and ask how such a small tale could possibly be stretched into three films - the same amount of films as Jacksons original trilogy. The actual thing to think about here is when the events of The Hobbit take place, and the period of time between it and the Lord of the Rings books.
Smaug is killed and the Battle of the Five Armies is waged against the Goblins and Wargs during the year 2941 of the Third Age. That means that there is a gap of 59 years from when Bilbo returns to The Shire with The One Ring and when he decides to leave The Shire again on his 111th birthday in TA 3001. The events of what take place in these years are well documented, and could actually be included as a third movie in the series that would very effectively bridge the gap between the two trilogies.
First we have the story of Bard rebuilding the Valle and Gollum leaving the mountains to begin his hunt for the thief Baggins in the year 2944. In the year 2951, Sauron declares his presence in Mordor and a 20 year old Estel (Aragorn) comes of age under the care of Elrond after his father was killed when he was two years old. It is at this time that he is told of his heritage and gives him the Ring of Barahir and, the well known Shard of Narsil. He also meets and falls in love with Arwen at this time before he sets of the become the Chieftain of the Dunedain and the Rangers.
In 2453 The White Council meet and Saruman (already s meet and Saruman insists that the One Ring has been swept out to sea, but actually kept a watch of Gandalf and his activities and sent spies to the Shire, searching for the ring himself). Three years later Gandalf first meets Aragorn and they become close friends and it is at this time that Aragorn and the Rangers keep watch on The Shire, and he becomes known as Strider.
For 23 years Aragorn sets off on many journeys serving the armies of Rohan and the Steward of Gondor (in disguise under the name of Thorongil) - raising morale to counter the threat of Sauron, leading an assault of the rebel province of Umbar in 2980, and then suddenly left to return East. In the same year Arwen pledges her hand in marriage to Aragorn and Frodo Baggins loses both of his parents in a boating accident, falling under the care of Bilbo sometime later.
In 2989 Balin, as we know leads a company of Dwarves to recolonise Moria and is killed five years later along with the rest of the Dwarf colony in the Chamber of Mazarbul (as we are told during the events in Lord of the Rings).
Starting in 3009, and for an interval of eight years, Gandalf and Aragorn begin their search for Gollum and he is finally captured by Aragorn in the Dead Marshes in 3017 where he is taken to Thranduil in Mirkwood to be questioned about the One Ring and his hunt for Bilbo. He is guarded day and night until eventually the Elves take pity on poor Gollum and allow him to climb a lone tree. One night in June of 3018 Gollum refuses to come down from the tree and that night the Wood-Elves are attacked by Orcs and Gollum escapes. It is at this time that Legolas Greenleaf, son of King Thranduil is sent to Rivendell to inform Elrond of Gollum's escape and arrives shortly before the events of October 25th, 3018 where he is chosen to represent the Elves in the fellowship to accompany the Ring-Bearer.
Now, try and tell me that there isn't enough material to easily cover a third movie! Peter Jackson, in my opinion, showed great respect for the original material, and I'm sure he will do the same with the Hobbit.