In 2008, the site launched its first local version, HuffPost Chicago; HuffPost New York launched in June, 2009, HuffPo Denver launched on September 15, 2009, and HuffPo Los Angeles launched on December 2, 2009. The Huffington Post has an active community, with over one million comments made on the site each month. Prior to The Huffington Post, Huffington hosted a website called Ariannaonline.com. Her first foray into the Internet was a website called Resignation.com, which called for the resignation of President Bill Clinton and was a rallying place for conservatives opposing Clinton.

In addition to columns by Arianna Huffington and a core group of contributors such as Harry Shearer, John Conyers, Rosie O'Donnell, and Roy Sekoff, Founding Editor, The Huffington Post has over 3,000 bloggers—from politicians and celebrities to academics and policy experts—who contribute in real-time on a wide-range of topics.

A comprehensive list of contributors to The Huffington Post blog can be found in its "Bloggers Index, but includes: Greg Gutfeld, Barack Obama, Hillary Clinton, Heather Robinson, Michael Moore, Jimmy Demers, Madonna, Alec Baldwin, Norman Mailer, Saskia Sassen, Sheryl Sandberg, John Cusack, Larry David, Nora Ephron, Madeleine Albright, Robert Redford, Anneli Rufus, Neil Young, Rahm Emanuel, Albert Brooks, Mia Farrow, Russ Feingold, Al Franken, Ari Emanuel, Gary Hart, Edward Kennedy, Joshua Kors, John Kerry, Nancy Pelosi, Jamie Lee Curtis, Ryan Reynolds, Richard Patrick, Craig Newmark, Donna Karan, Kenneth Cole, Ryan J. Davis, Jason Pinter, Donatella Versace, Bill Maher, Cleo Paskal, B.D. Gallof, Lutfullah Kamran, M. K. Asante, Jr., David Helfenbein, Robert Wright, Larry Gelbart, Stephen Covey, Wendy Diamond, Azar Nafisi and Sadhguru Jaggi Vasudev.

The site also publishes columns by specialists in a wide range of fields such as Alice Waters on food, Doctor Harold Katz on dental health, Suzie Heumann on sex, Diane Ravitch on education, Jacob M. Appel on ethics, and Jon LaPook on medicine, publishes scoops of current news stories and links to selected prominent news stories, and provides a liberal counterpoint to sites such as the Drudge Report. Compared to other left-wing blogs such as Znet or Daily Kos, The Huffington Post offers both news commentary and coverage.[citation needed] The comment section is home to discussions on politics, religion, and world affairs.

The Huffington Post's OffTheBus is a citizen-powered online news organization that is a collaboration between The Huffington Post, New York University (NYU), and Jay Rosen's NewAssignment.Net. The Huffington Post's FundRace is a website that tracks contributions to the presidential campaigns and includes a mapping feature that shows contributions broken down by city, neighborhood, and block.

In August 2006, The Huffington Post announced that SoftBank Capital would invest $5 million in the site, which had grown in popularity in only a year, to help expand it. Plans included hiring more staff to update the site 24 hours a day, hiring in-house reporters, and a multimedia team to do video reports. Alan Patricof's Greycroft Partners also invested. The news marked the site's "first round of venture capital funding."

The site now has invested in Vlogging, or video blogging, with many of the site contributors contributing via video, and capturing clips in the media and posting them on the site.

In November 2008, The Huffington Post completed a $15 million fundraising from investors. The money will finance expansion including more journalism and the provision of local news across the United States.