I’ve been less than prolific on Postcards lately. Pardon the layoff–it’s temporary. And it’s just because I’ve been running around working on what is going to be, I think, Fortune‘s best Most Powerful Women issue yet.

The issue, our 13th since we began the act in the magazine in 1998, will hit newsstands on Monday, October 4. That’s also the day we begin the Fortune Most Powerful Women Summit, which is in Washington, D.C. this year for the first time ever. This week, Hillary Clinton confirmed as a keynote speaker. On Wednesday, October 6, the Secretary of State will be interviewed by Ann Moore, the chairman and CEO of Time Inc. , Fortune‘s parent.

Elizabeth Warren, the consumer-protection advocate just named to a key post in Treasury, also joined the Summit program this week. She’ll be on a panel called “The Enforcers.” The other Enforcers in this session: FDIC boss Sheila Bair, SEC chairman Mary Schapiro, and Justice Department Antitrust chief Christine Varney.

This year’s gathering of 400 includes a record lineup of Fortune 500 CEOS. Including: Indra Nooyi of Pepsico , Irene Rosenfeld of Kraft , Andrea Jung of Avon , Ursula Burns of Xerox , Angela Braly of WellPoint , Pat Woertz of ADM , Ellen Kullman of DuPont , Carol Bartz of Yahoo . And one guy who has become a Summit regular: Warren Buffett is coming back to share his wisdom and outlook with Fortune‘s own Carol Loomis.

Another MPWomen Summit regular is uber-analyst Meredith Whitney. She’s one of the more popular people I write about on Postcards (big traffic whenever I mention her). So I must share this C-SPAN interview that Whitney did last week. In fact, if you scan to minute 13, you’ll catch her talking about the MPWomen list and Summit. “There are so few women on Wall Street,” she says, as if to explain why she likes hanging with other powerful women. About Wall Street, she says, “I call it a man zone.”

Though this year, we do have a few others from Wall Street who will be with us. Besides Whitney, they include Bank of America wealth management chief Sallie Krawcheck and hedge fund owner Zoe Cruz, ex-Morgan Stanley . Cruz has been under the radar since losing her job as co-president in late 2007 over huge trading losses.

More than ever on Wall Street, it’s survival of the fittest. (Just ask Oliver Stone.) Last week, Whitney predicted that employment on Wall Street will drop by 10% between now and early 2012. For three years, she’s been making bearish calls on the financial-services industry and overall economy. Whitney’s only recommended stocks today: Visa , Mastercard , and Jeffries .