From Guardian Unlimited:

The Tolkien community was in hysterics yesterday. At least that was the verdict on one of the leading Hobbit websites following the announcement in Los Angeles that Peter Jackson, director of the $3bn-plus trilogy The Lord of the Rings, had signed up to produce two films based on The Hobbit, expected to go into production in 2009.

Story here. The Hobbit will be split into two films, tentatively scheduled to release in 2010 and 201. No director has been chosen yet - Peter Jackson is too busy with other projects, according to an article in stuff.co.nz. Presumably, the leading website mentioned is TheOneRing.net.