(Fortune) -- Oprah Winfrey, Chairman of Harpo Inc., ranks No. 8 on Fortune's 2006 list of 50 Most Powerful Women.

Move over, Howard Stern. Oprah took to the radio waves in September with the launch of Oprah & Friends, an XM Satellite Radio network. In January her $40 million Leadership Academy for Girls will open in South Africa.

By the key criteria Fortune uses in assembling its annual list - the size, importance, and health of each business in the global economy, and the momentum of each woman's career (along with her social and cultural influence) - there's no question that the power of women in the corporate sphere is rising.

Indeed, it could be called the year of the Most Powerful Woman CEO. The top seven positions on Fortune's 2006 Most Powerful Women list are held by CEOs. CEOs on this year's list include Ann Moore of Time Inc (Charts).; Susan Ivey of R.J. Reynolds Tobacco (Charts); Shelly Lazarus of Ogilvy & Mather Worldwide (Charts); Mary Sammons of Rite Aid (Charts); Paula Rosput Reynolds of Safeco (Charts); Christina Gold of Western Union (Charts); Stacey Snider of DreamWorks SKG (Charts).

Next: Full list: 50 Most Powerful Women at //money.cnn.com/popups/2006/fortune/mostpowerfulwomen/1.html

Plus: Most Powerful Women: 10 Highest-Paid at //money.cnn.com/popups/2006/fortune/womenpay/index.html