In Pokémon Diamond and Pearl, there are over a hundred new Pokémon, many new Berries and items, along with the use of the Nintendo DS's touch screen for ease of use and wireless communications between DS's. There also is the new WiFi conection that Nintendo has set up for battling and trading for players all over the world.
Also added was the Underground, a multiplayer area where people in range of each other are able to use their Explorer Kits to go underground and retrieve items such as fossils to reconstruct Pokémon in Oreburg, plates that enhance certain types of moves, and even make their own secret base to play "capture the flag" with others in their area.
Currently, in the US, UK, and Japan, there are two versions out, Pokémon Diamond and Pokémon Pearl. There is a newer game entitled Pokémon Platinum, released 22nd March for US and 22nd May for Europe. It continues in the Pokémon series where Diamond and Pearl left off.