Blizzard announced today that they will begin offering the Starter Edition of Diablo III free of charge. Up until now, the Starter Edition was available only in the beta, to players waiting for their online payment to clear, and players accessing the game via one of the guest passes found in retail packages.
Starting today, players will be able to download the free game client from Battle.net (or from a friend's game disc). The Starter Edition will allow players access to the first level of the game including the first major boss, the Skeleton King, and will allow them to reach level 13.
There are restrictions that come with the Starter Edition though. No achievements will be granted until you unlock the full game (though your progress will still accumulate.) There is also no access to the Real-Money Auction House.
Diablo III is Blizzard's third game to come around to this "Starter Edition" strategy. StarCraft II features a similar system which gives access to some of the campaign missions, and World of Warcraft now grants free access up to level 20.