The Online News Association, the world’s largest membership organization of digital journalists, today announced Twitter CEO Evan Williams and Blogher co-founder Lisa Stone will be keynote speakers at its conference October 1-3 in San Francisco.

The 2009 Conference and Awards Banquet, which marks ONA’s 10th anniversary, is expected to attract hundreds of online journalists from around the world for three days of training, panels and workshops on emerging trends, as well as a Career Summit and expanded Job Fair. Last year’s event in Washington, D.C. sold out.

“ONA’s conference is where journalism meets technology,” said ONA President Jonathan Dube, “and this year we’re especially looking forward to hearing from two people who are revolutionizing the way journalists do their jobs.”

Williams is the CEO and co-founder of Twitter, a social network where users answer the question, “What are you doing?” in 140 characters or less. Begun as a side project less than three years ago, Twitter now reaches an estimated 5 million users and is ranked as a top social site. It is also being adopted as a reporting tool, with users filing everywhere from the Mumbai bombings to the Academy Awards’ red carpet. Williams also co-founded Blogger, a service for creating and managing blogs, and is credited with inventing the term “blogger.”

Stone is the CEO and co-founder of Blogher, an online community for women. Begun as a labor of love in 2005 as a conference for women bloggers, Blogher is now the number-one community of blogs by women, reaching more than 14 million women each month via annual conferences, a Web hub, and a publishing network of more than 2,700 blog affiliates. The former VP of Programming and editor-in-chief of Women.com, Stone has launched blog networks and interactive programming for Hearst, Rodale Magazines, Knight-Ridder Digital and Glam media. She is the first internet journalist awarded a Nieman Fellowship by Harvard University.

The Online News Association’s mission is to inspire innovation and excellence among journalists to better serve the public. The membership includes news writers, producers, designers, editors, bloggers, technologists, photographers and others who produce news for the Internet or other digital delivery systems, as well as academic members and others interested in the development of online journalism. ONA also administers the Online Journalism Awards.