Betsy Morgan is out as CEO of HuffingtonPost.com — and her firing came as a surprise to her, Morgan told me when we connected by phone late this afternoon.

“Bummer.” That was the first word she uttered in our conversation. Morgan says she’s not bitter, however. After all, what a ride Arianna’s web venture has been these past 20 months. Morgan joined in October 2007 — and I remember it well because she was at the Fortune Most Powerful Women Summit as the news of her hiring hit the papers. Just hours after Arianna Huffington, Morgan’s boss, introduced her new CEO to the 300 women leaders gathered in California, Morgan was called back east. Her mother had died suddenly.

It was a dramatic start of a dramatic 20-month ride. Back in the fall of 2007, HuffPo, as the site has come to be known, was attracting 1.2 million unique visitors a month. This past April, it drew 5.6 million uniques, according to ComScore. While traffic more than quintupled, revenues doubled. The Huffington Post morphed from a political to a mainstream site. And the company, which has raised some $35 million, is edging toward profitability.

Replacing Morgan as CEO is Softbank Capital’s Eric Hippeau, a media-industry venture capitalist who has been on the HuffPo board since 2006. Morgan could have stayed at the company in a lesser role, but she doesn’t want to do that. So, what’s next? She’s asking herself. “My biggest question is,” she told me, “Do I help fix an old media business or do I help grow a new one?”

Having joined HuffPo from CBS , where she ran CBS News’ digital arm, Morgan knows both sides of the media business. “God, I’ve seen so much of that side where you invent differently and innovate differently,” she says. “But I also know so many media companies that have gone halfway into digital. Do I go help them with that?”

As she contemplates her future, she’ll attract her own traffic — headhunters, that is. Arianna may help her decide her next act. The parting between these two powerful women is neither pleasant nor easy, but it’s amicable. “I loved working with Betsy,” Huffington told me today. “We talked every morning at 7:30. It was always a partnership. And she was always a class act.”

Before Morgan and I ended our conversation, I asked her what she learned from the reigning diva of digital. “Arianna taught me that everything you do, you should do with passion and a sense of humor,” Morgan says. Oh, and one other thing, she said: “The sky’s the limit.”