Two more Most Powerful Women -- the latest, both named Linda -- are leaving big companies.

One is Royal Dutch Shell's (RDS.A) Linda Cook -- whose exit lends fresh meaning to the term "leaky pipeline." Cook, executive director at the Anglo-Dutch oil giant and No. 3 on Fortune's 2008 international Most Powerful Women list, will leave next Monday after losing the CEO race there, according to the Wall Street Journal. Strangely, the New York Times this past Sunday ran a first-person piece by Cook, 50, about her unlikely career path. She grew up in Kansas, was one of few women in engineering, and early on bunked with the boys in a mud loggers' trailer to get the job done at Shell.

And the other Linda who is leaving? That's Linda Dillman of Wal-Mart (WMT). EVP of Benefits and Risk Management and a multi-time star on Fortune's Most Powerful Women list, Dillman is departing the world's biggest retailer at the end of July. Yes, her exit is surprising -- and not. In 2003, Dillman told me that she questioned every promotion she got. "Promotions have come to me before I felt I was ready," she said. In 2002, when she was offered the CIO job at Wal-Mart, she replied, "Tell me what you're going to do if I don't take the job." The higher-ups persuaded her to accept the post.

Dillman, who isn't speaking publicly about her latest move, apparently wants to return to her roots: technology (and in her current lofty post, she wasn't doing what she loved). Given her recent experience in benefits and HR, some people think she might move into HIT -- health information technology. Hmm, maybe General Electric (GE), which is expanding aggressively in that area, would have an interest in Dillman.

Like a lot of accomplished women, Dillman defines power broadly -- with a global view: Over the years, she's been a standout mentor in the Fortune/U.S. State Department Global Women Leaders Mentoring Partnership. Dillman's 2009 mentee, Wilma Judish Appenteng, just returned to Ghana after spending three weeks in Bentonville, Arkansas. The folks in Bentonville and the star manager from Ghana, I'm told, opened each other's eyes to the world.