The site's arrival has generated huge media interest, with Kaper and House PR helping to fan the flames. There is clearly an appetite for the site this side of the pond - 1.2 million Brits already visit the US version - but will the UK version have the same pulling power?
Launched by Huffington in 2005, the original site has grown to command more than 38 million unique users a month (ComScore), has 9,000 bloggers that have included Barack Obama and Madonna, and was sold to AOL in February for $315m.
The UK launch is part of an international expansion plan that has seen a Canadian version launch in May, and others scheduled for launch this year.
The Huffington Post UK uses a similar format to the US, with ten paid editorial writers and an army of bloggers writing about everything from politics to entertainment. Staff journalists will feature the best posts on the home page.
Despite success in the US market, the UK site faces stiff competition from well-established national media outlets and popular blogging sites. PLMR MD Kevin Craig says the landscape is more competitive: 'The US site grew up with the rise of blogging globally, while the UK already has prominent bloggers on every topic.'
Andy Bull, multimedia journalist and former editorial director of AOL UK, agrees: 'It's questionable whether there's a gap for HuffPost UK. We already have excellent forums such as The Guardian's Comment is Free.'
The UK site's editor-in-chief Carla Buzasi says the famously liberal site will differentiate itself from other political sites in the UK by taking an open stance: 'We are not aligning ourselves with any party.'
To a large extent, the success of the site will depend on the quality of the bloggers, who are controversially unpaid.
So far, this does not seem to have affected the UK version, with more than 300 bloggers signed up at launch, including Sarah Brown, Ricky Gervais and Alastair Campbell. Others include Neville Hobson, WCG's former head of social media for Europe, now an independent consultant, and Save the Children staff.
Hobson says: 'The Huffington Post is a mainstream media outlet and a force to be reckoned with. I expect it will have a disruptive influence on the UK media market.'
Save the Children's digital media manager Liz Scarff says the site can help spark and continue debate. 'Blogging is a key tool for us. Communication has changed and it's key for us to tell our stories in real time.'
Craig believes the site will be a success: 'The PR potential is huge. I'm sure it'll form robust filters.' But he adds: 'The Huffington Post in the UK cannot afford to put a foot wrong.'
Total unique users: 36 million on the US site (ComScore June 2011)
UK users: 1.2 million visit the US site
Sale: $315 in February 2011 to AOL
Contact: Blogs firstname.lastname@example.org
Carla Buzasi Carla@huffingtonpost.com
A MINUTE WITH ... Carla Buzasi, editor-in-chief, The Huffington Post UK
How will the site differ in the UK?
The UK version will have its own content, but we will lean on the US site where relevant. For example, if we are covering the US elections, we will go to our US writers. Equally, they will have access to our London journalists.
How will the site tie in with other AOL brands?
We will be drawing on content from our other sites such as MyDaily for style content. So PROs should make sure they are still working on relationships with journalists at existing sites.
Who reads The Huffington Post?
The 1.2 million Brits that currently visit the US site are high spending, media savvy 20- to 30-year-olds. In the US the audience is slightly older. We are interested in feedback. We expect to launch a second version of the site by September.
How can PROs get involved?
They can sign up as bloggers or speak to our journalists. For example, this morning, Save The Children got in contact. They have staff blogging in projects in Africa. I know the team and can give them a log-in to the site.
What advice do you have for PROs?
PROs writing blogs should put themselves in the shoes of the readers and think like a journalist; what's going to make people want to share my post with friends?