It's no secret that "Words With Friends," Zynga's word-building game, is popular among celebrities. Just ask Alec Baldwin.

And starting Thursday, celeb wordsmiths like Kristen Bell, Edward Norton and Snoop Lion will play the Scrabble-like game for a cause.

In addition to bragging rights, players are taking part in Zynga and American Express' "Words With Friends" Celebrity Challenge for the chance to win $500,000, which they'll donate to the charity of their choice, according to a press release.

Fans can get in on the action by playing "Words With Friends" on behalf of their favorite celebrity, or by donating to one of eight charities through CrowdRise, a fundraising site founded by Norton.

"We are all about making fundraising fun through competition and games at CrowdRise, so this couldn't be a better partnership for us," Norton said in a press release. "Zynga knows a thing or two about social gaming, and it's awesome to see them using that knowledge to engineer impact."

Other celebrities taking part in the tournament, which runs through October 3, are Jonah Hill, John Legend, Eva Longoria, Paul Pierce and Sophia Bush.