If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast nonland cards as though they had flash. (You may cast them any time you could cast an instant.)
8/15/2010 Your "opening hand" is the hand of cards you decide to start the game with after taking any mulligans.
8/15/2010 After all players have decided not to take any more mulligans, if the starting player has any Leylines in his or her hand, he or she may put any or all of them onto the battlefield. Then each other player in turn order may do the same.
8/15/2010 Leylines that start the game on the battlefield aren't cast as spells. They can't be countered.
8/15/2010 After each player has exercised his or her option to put Leylines onto the battlefield, the first turn of the game begins.