There are six different sets:
79000 – Riddles for the Ring, 105 pieces, $9.99
79001 – Escape from Mirkwood Spiders, 298 pieces, $29.99
79002 – Attack of the Wargs, 400 pieces, $49.99
79003 – An Unexpected Gathering, 652 pieces, $69.99
79004 – Barrel Escape, 334 pieces, $39.99
79010 – The Goblin King Battle, 841 pieces, $99.99
There are also talks about more sets in the Lord of The Rings series coming in 2013, as are surely additional sets in the Hobbit series when the next movie in the Hobbit trilogy is released in December 2013.
When I visited Toys”R”Us today, I found a small set not listed on the Lego website. It does not have a name, but the 31 piece set has the number 30213 and contains Gandalf with a map, a sword and a small part of a ruin with a skull, a torch and a spear. It comes in a small plastic bag, just like the Bilbo with fireplace set that was available for a while this fall.