This week, Toy's R Us is offering a Buy 2 DS games special. If you buy two games at the same price you get a third equally price (or less than) DS game free. Until this Saturday, both online and in stores are offering this deal.
For those of you who have not purchased Diamond and Pearl, this is the week to buy it. If you buy both Diamond and Pearl you can get either Pokemon Trozei, Pokemon Mystery Dungeon Blue or Pokemon Ranger for free.
Just add three games to your shopping cart and it will automatically set the third games price to free.
Source: http://www.toysrus.com/shop/index.jsp?categoryId=2255974