Billionaire Warren Buffett announced Monday that he donated $3.6 billion worth of Berkshire Hathaway stock to the Bill & Melinda Gates Foundation and four other charities. Buffett, 88, nicknamed the "Oracle of Omaha," will convert 11,250 of class "A" Berkshire shares into 16.9 million class "B" shares, Berkshire Hathaway said in a news release. Besides the Gates Foundation, the recipients will be the Susan Thompson Buffett Foundation, the Sherwood Foundation, the Howard G. Buffett Foundation and Novo Foundation. With prior Buffett donations, the longtime Berkshire chief will have given about 45 percent of this 2006 holdings to the five foundations for a total of about $34 billion.