The world’s greatest investor and the Goldman Sachs (GS) CEO will be at our opening dinner tonight. It’s a crazy coincidence since we invited these two men (our first time inviting men) months ago. Then, last week, the wealthier of the two invested $5 billion in the other one’s company. This evening will be a chance for Buffett and Blankfein to chat with each other about the little deal that helped shore up the global financial markets at a critical time.

Tonight, Blankfein will present the first Goldman Sachs/Fortune Global Women Leaders Award to two alums of an international mentoring program that Fortune, through this Summit, runs in partnership with the U.S. State Department. Then, on Thursday morning, my colleague Carol Loomis will interview Buffett on stage.

All week on Postcards, you’ll read insights and stories from the Summit. Besides those lucky guys who are in attendance (Buffett, Blankfein, and my boss, Fortune managing editor Andy Serwer), we have lots of women who are on the just-released 2008 Most Powerful Women in Business list. Our lineup includes: ADM CEO Pat Woertz (ADM), Procter & Gamble (PG) global business units president Susan Arnold, and Xerox (XRX) president Ursula Burns. Thursday evening, 300-plus women leaders will watch Sarah Palin face off against Joe Biden in the VP debate — then dinner, Wii Olympics (Meg Whitman against Martha Stewart in Wii baseball?!) and bridge with Buffett for those women who might muster the courage to compete with the Oracle of Omaha. Melinda Gates will also be with us. So will PepsiCo (PEP) CEO Indra Nooyi. She’ll be chatting on stage with Ann Moore, the CEO of Time Inc., Fortune‘s parent.

Also with us: all 15 of the powerful women of Silicon Valley whom I featured in my story, “The New Valley Girls” in Fortune‘s just-released Most Powerful Women issue. It’s amazing to me that all 15 are here, but their presence attests to the theme of the story, which is: Today’s rising-star women in tech not only know one another, but they help each other in their careers and their businesses; meanwhile, many are building social-networking companies to facilitate that very connectedness. Click here to see a cool interactive chart featuring these well-connected 15 powerful women. And enjoy all the coverage on Postcards!