It looks like March 5th is the actual anniversary date, and that day will bring a slew of deals on various Google Play content. We know this because March 5th has already begun in countries on the other side of the world like Australia and New Zealand. We can't say yet exactly what the deals will be, because they could change based on your location, but it is fair to assume there will be free and reduced prices on apps, games, books, magazines, music, and video. You know, essentially all of the categories in the Play Store (though we don't expect hardware deals).
As the date crosses over to March 5th, you can check to see if the deals have begun using the link below. And, we'll be sure to update you all with the various deals available in the U.S. when the time comes.