Millions of dollars have been pouring into charities in the past few days, amid growing criticism of the official response to the crisis. One estimate said at least $100m (about £54m) had been donated or pledged by individuals and businesses by Thursday.
People are also offering other types of aid. Classified advertising website Craigslist.com is carrying countless postings from people from Arizona to New York offering to put up families displaced by the hurricane in their homes.
Colette Chamberland and her husband Michel in Riverview, Florida, have posted an ad offering space in their home to a family of four.
"I am ashamed at how our country has handled this whole situation," she said. "I am a mother of three girls and I hope someone would do the same for my family. It breaks my heart to see these women with babies, crying and having nowhere to go."
Other postings offered transport to stranded people; a doctor was looking for fellow medical professionals to form an emergency team; stables were offered for horses; organisers were looking for bands for charity events and a certified diver in Florida said he would be willing to look for bodies in the city's flooded streets.
Celebrities have also responded. The hip-hop stars Sean "Diddy" Combs and Jay-Z pledged $1m to the American Red Cross and said they hoped to inspire others to do the same. "This is our community," said Jay-Z. "When I turn on CNN, I see a lot of black people on the streets."
The singer Celine Dion also pledged $1m.
A series of celebrity-studded telethons is planned. NBC cleared its schedule last night for a show featuring Harry Connick Jr, Leonardo DiCaprio and New Orleans native Wynton Marsalis. The big television networks were planning a simultaneous broadcast for Tuesday. MTV is planning its own money-raising event on September 10.
The volume of donations was expected to match the outpouring after the tsunami in Asia, when $1.5bn was given, and the terrorist attacks on the United States of 2001, when $2.7bn was raised.
As of Thursday, the American Red Cross said it had received almost $72m but that figure will have grown significantly since then.
"This is our largest mobilisation ever," a spokeswoman said.
Among the corporations lending support, Rupert Murdoch's News Corporation announced a $1m pledge to the Salvation Army; the energy firm Chevron is giving $5m; BP is giving $1m and matching employee contributions; the retailer Target is giving $1.5m and helping with distribution of goods like bottled water, energy bars and insect spray. United Health group is giving $10m; Wal-Mart and Exxon have given $2m each.
Companies have also offered other kinds of assistance. Kellogg has sent seven lorry loads of NutriGrain bars and other crackers and biscuits to the area, and U-Haul offered 30 days' free storage for people affected by the hurricane.
There has also been cash and aid coming from about 20 countries, including El Salvador, China, South Korea and the United Arab Emirates.
The Australian government announced a A$10m (£4.1m) donation, Germany offered mobile medical units, Sweden water purifying equipment and emergency shelters, and Japan tents, blankets and generators.
The UN Office for the Coordination of Humanitarian Affairs said it had a taskforce on standby.
Tony Blair said Britain was ready to help if asked. "The whole of this country feels for the people afflicted," he said in London. "We want to express our sympathy and our solidarity and give our prayers and thoughts."
