News from Nvidia and quoted from www.worldofwar.net:

Great news from Nvidia today as they announce a further 1000 Beta slots are up for grabs through their Nzone website. NVIDIA and Blizzard are working together to ready the game for play on NVIDIA graphics processing units (GPUs), the preferred graphics hardware platform for World of Warcraft. The companies will also engage in strategic co-marketing activities as part of NVIDIA's "The Way It's Meant to Be Played" programme. To celebrate the collaboration, NVIDIA and Blizzard will randomly distribute 1,000 closed beta accounts to eager gamers hoping to be among the first to experience the game. Sign-ups will be held for one week only, starting today at Nzone.

As part of NVIDIA's The Way It's Meant to Be Played programme, World of Warcraft will undergo extensive compatibility testing to ensure a "no hassles" install-and-play experience for gamers equipped with NVIDIA GPUs. Blizzard has optimised the game for NVIDIA hardware and is working with NVIDIA to ensure the game plays well across a broad line-up of GPUs, from the brand new GeForceTM 6800 series to the GeForce 2. "The investment we're making with Blizzard in compatibility will pay out in spades as soon as the legions of gamers go from install to play quickly and effortlessly," added Rehbock.

A heads-up that the sign-ups are not yet live so I'm afraid you will just have to keep checking the site for an update :)