10/1/2009: Gaea's Touch lets you play an additional land during your turn if it's a basic land and it has the land type Forest. (The two such cards are Forest and Snow-Covered Forest.)
10/1/2009: If you play a basic Forest during your turn, you must declare whether you're using your standard land play or Gaea's Touch's first ability to do so.
10/1/2009: If you play a land using Gaea's Touch's first ability, and then Gaea's Touch leaves the battlefield (because you activated its second ability, for instance), the land you played still counts as an additional land play for the turn. If you haven't already, you can still play a land using your standard land play.