The U.S. Open begins today at the USTA Billie Jean King National Tennis Center. So what could be more fitting than a Guest Post on Postcards from Billie Jean King herself? It's fitting too because King, ranked No. 1 in the world five times during her legendary career, has odd and interesting connections to some of the CEOs on Fortune Most Powerful Women in Business list.

This May, at a Most Powerful Women dinner in New York City, I happened to run into King and Andrea Jung, the chairman and CEO of Avon (AVP), just as the two women were leaving. "Do you know each other?" I asked. They didn't. King proceeded to tell Jung and me that when she was growing up in Long Beach, Calif., her dad was a firefighter and her mother a housewife who sold Avon products. The family struggled financially, and it was the extra income from Avon that enabled Billie Jean and her brother, Randy, to pursue their sports dreams in tennis and baseball. Randy went on to be a major league baseball player and Billie Jean went on to win 39 Grand Slam titles, including a record 20 championships at Wimbledon.

Then there's Time Inc. CEO Ann Moore's fateful BJK connection. Moore met her husband, Donovan, at a dinner party on the night in 1973 when King beat Bobby Riggs in the signature battle of the sexes. "I left the dinner table to go watch the match," Moore recalls. "Donovan snuck away too. We were the only two who watched. Everyone else stayed and finished dinner." I often hear Moore use King's mantra: "Pressure is a privilege." Good thing she embraces it, as Moore is the boss of the world's largest magazine company (Fortune's publisher and a unit of Time Warner (TWX) at a particularly challenging juncture).

I've come to know Billie Jean King over the years, as she's become a regular at Fortune's Most Powerful Women Summit. (She even gave tennis lessons to our participants last year.) King is a kick. Having lunch or simply a chat with her is like volleying at the net. She pummels you with ideas and questions, rat a tat tat! And even though she is the all-time icon of women's sports, she never gets too comfortable in her position. Power, she once told me, is all about reaching out horizontally to make an impact in various ways. That's why, I guess, she's behind the creation of the Virginia Slims tennis tournament (signing a $1 contract to launch the first pro women's tour in 1970), the Women's Tennis Association, the coed World TeamTennis league, and the Women's Sports Foundation -- fighting for equal pay for women athletes all along the way.

Now she's collecting more laurels -- not only the U.S. Open's Billie Jean King Tennis Center, but also a Billie Jean King International Women's Sports Center at Manhattan's new Sports Museum of America. Rest on her laurels? No way. In her new book, Pressure is a Privilege, she passes on all sorts of lessons about extending power and influence. As she says in her Guest Post here on Postcards, bring all of yourself to everything you do. Click here to read more.