By Steve Kingstone
BBC South America correspondent in Porto Alegre, Brazil
"The American army in Iraq has a disproportionately high percentage of black and Latino soldiers," proclaims a highly-energised speaker.
The prevailing mood has been light-hearted and peaceful
"It's like when the Romans recruited barbarian tribes to defend their empire."
In a nearby tent, an anti-globalisation campaigner is teaching a cosmopolitan audience how to mount a media campaign.
His English words are translated by volunteers into French, Chinese and Swahili.
And further on, participants are arriving for a workshop entitled: 'Improving social and environmental standards in the tea industry.'
Welcome to the World Social Forum - a multi-coloured umbrella event which brings together every cause imaginable.
Between them, more than 100,000 delegates are taking part in over 2,000 debates and activities.
"It's one-stop shopping for the Left," says Suren Moodliar from Boston, whose focus here is the outsourcing of jobs.
"You bump into people covering a wide range of issues, but you quickly find an underlying area of agreement."
"I'm learning a lot," says Barbara Salvaterra, a Brazilian who works with the country's landless movement.
"The workshops are very interactive and people discuss political issues openly - without worrying about offending anyone."
Marley and Lenin
The forum is taking place on the shores of Porto Alegre's Guiaba lake.
Eleven thematic "terrains" have been constructed as venues for debates.
In the spirit of the event, some 25,000 participants have pitched tents at a central 'Youth Camp.'
Che Guevara, Bob Marley and Vladimir Lenin stare down from posters, as bikini-clad women use the communal showers. Other campers hang out in a "solidarity tent".
But the spirit of capitalism is alive here too.
In the form of busy young Brazilians hawking hot-dogs, water and sun-hats.
As the camp warms up - to 38C - so does their trade.
The overwhelming mood of the Forum is laid-back and peaceful, but the police have had some cause for concern.
On Friday they raided a local house, finding dynamite and Molotov cocktails.
Forty-three youths, described as squatters, were detained.
The police say they were planning an attack on the Forum.
The youths reportedly claimed to have been threatened by skinheads.
More intriguing is a security debate, centring on the dress sense of Brazil's President, Luiz Inacio Lula da Silva.
In soaring temperatures, Lula addressed the Forum on Thursday - receiving a hostile reception from a small number of left-wing demonstrators.
All types of causes are being aired at the event
Despite the heat, he persisted in wearing a jacket zipped-up to the neck. And at times he was seen to move awkwardly.
That prompted speculation that the president was wearing a bullet-proof vest - a claim which has been vehemently denied by his Workers Party.
"I watched him put on his shirt and jacket," government minister Luiz Dulci told the Porto Alegre newspaper, Zero Hora.
"We knew he would face hostility, but it's not in the nature of these people to commit murder."
For the foreseeable future, this will be the last World Social Forum to take place in Brazil.
Next year, events will be staged in a variety of countries rather that at a single venue.
And in 2007 the gathering will move to Africa, with a host city still to be confirmed.
Delegates deny that the Forum is running out of steam, having seen many of its ideas copied by the rival World Economic Forum in Davos, Switzerland.
"Slowly Davos is starting to increase its involvement in these issues, but the Social Forum remains an important source of pressure," says Salil Shetty, director of the United Nations' Millennium Development Goals Campaign.
"Its work is crucial and it's going to carry on."