The Deputy Prime Minister met emergency services workers and was shown inside the safety cordon at the Clutha bar in Glasgow where tragedy struck on Friday night.
Nine people, including three on board the helicopter, died when the aircraft fell from the sky "like a stone".
More than 100 people were inside at the time.
Mr Clegg laid flowers at the nearby memorial site and met members of the community to discuss the incident.
All nine people who died have been identified.
Robert Jenkins, 61, and Mark O'Prey, 44, both from East Kilbride in South Lanarkshire, 33-year-old Colin Gibson, of Ayr, South Ayrshire, and John McGarrigle, 57, from Cumbernauld in North Lanarkshire, were named early this morning.
Two other victims killed inside the pub had earlier been named as 48-year-old Gary Arthur, from Paisley, and Samuel McGhee, 56, of Glasgow.
All three of the helicopter's crew died as it returned from a police operation at 10.25pm on Friday. They were pilot David Traill, 51, and Kirsty Nelis, 36, and Tony Collins, 43.
Eleven people remain in hospitals across the city.
The wreckage of the three-tonne Eurocopter was removed from the building yesterday which allowed emergency services to search the area inside the pub.
The site is still subject to a police investigation but management of the incident scene has been handed over to the city council.
Mr Clegg said: "The city is united in sadness and grief but also united in very heartfelt sympathy for those affected by the terrible events on Friday night, and also united in unequivocal support for the exceptional job done by the emergency services who have worked tirelessly in very difficult circumstances, and have also had to mourn, or are mourning the loss of their friends and colleagues."
He added: "I just think it is exceptional how everybody has reacted.
"This has touched everybody, every family and every individual."
He said the UK Government stands ready to provide help if and when it is needed.
"Well it's awful, but sometimes the very best in a community is brought to light when it faces the very worst, and I think that's what we've seen over the last few days in Glasgow," Mr Clegg said.
"I think the whole country is full of admiration for the community spirit which has come to the fore because this is a city united in grief but also absolute compassion and support for the exceptional work of the emergency services.
"I've spoken to a number of people involved in the operation and this is not only very physically tiring but also very emotionally draining."
On the investigation into the crash, he said: "We're not going to get instant answers. We just need to be patient to allow all the analysis and investigations to be done by the relevant authorities so that everybody gets answers in the weeks and months ahead to all the questions that everybody has got about how on earth this happened on a Friday night in such a popular pub here in Glasgow."
Air accident investigators have said the helicopter pilot made no mayday call and that no black box data recorder was on board.
Meanwhile, Scotland's First Minister, Alex Salmond, visited the City Chambers to sign the book of condolence.
More than 650 people, including survivors, children and students, have signed the book.
Mr Salmond said: "I had a look at some of the messages when I was able to sign the book today and people are expressing sympathy, condolence obviously, as you would expect, but also solidarity.
"The theme running through the messages is one of solidarity. The citizens of Glasgow grouping round those who have suffered loss or injury and showing that they care, and the people of Scotland grouping round the citizens of Glasgow - it's solidarity that runs through the book of condolence.
"Both in terms of the citizens, the ordinary people of Glasgow, and in terms of the work of the emergency services over these last few appalling days, that response has been terrific.
"People are not defined by tragedy - tragedy is a part of the fabric of life, even appalling disasters like the one that we've experienced.
"People are defined by how they respond to tragedies. That applies to people and families and cities and countries and in the response of the citizens of Glasgow, the response of our emergency services, even in this moment of calamity we can all walk that bit taller from knowing how Glasgow and Scotland has responded to this extremity."
He said an interim report on the incident from the Air Accidents Investigation Branch (AAIB) could be ready within a week but that the final report may take many months.
David Goodhew, assistant chief officer with the Scottish Fire and Rescue Service, was also at Glasgow City Chambers, where he met Mr Salmond.
Speaking of the tragedy, he said: "When the crews turned up it was chaotic, frightening for members of the public.
"Initially the crews had to establish what had happened. They had to immediately render assistance to members of the public and those who were injured, chaperoning people from the building, rescuing people from the building, getting as many people out as quickly as possibly because they were unsure what they were facing.
"There were fears a fire could have started.
"It's been a very difficult and delicate operation throughout. I think the fact that there were so many people trapped in the building... it was harrowing in lots of ways for the emergency services, searching for emergency service colleagues as well but the fire crews, ambulance crews, police crews and everybody concerned worked seamlessly for a single aim in order to resolve the incident as soon as possible and rescue people that could be rescued and recover people that unfortunately had perished in the incident.
"In many ways you would think the emergency services were working as one."
Mr Goodhew added: "It's difficult when it's large numbers of people trapped and rescued but their professionalism takes over. They're trained to do it over a number of years and they've attended many incidents - nothing as harrowing or dramatic as that but instinct kicks in, their professionalism kicks in and they work together to achieve a common goal, which is to render assistance and save lives.
"It could have been far worse in many ways. There were a large number of people in the pub when the helicopter crashed. Fortunately lots of those got out. Lots of those were rescued by members of the public, which was fantastic, and the reality of it is there could have been a fire. Fortunately there wasn't and the fact that there wasn't a fire obviously saved many more people."
Mr Clegg and Scottish Secretary Alistair Carmichael both advised against speculating on what caused the crash or on wider helicopter safety.
Speaking after his visit to St Andrew's Cathedral, where he met members of the local community, Mr Clegg said: "Until we know what happened to that particular helicopter on that particular day at that particular time, it is extremely difficult to make wider judgments about what reviews might be necessary.
"No one should have a closed mind when it comes to public safety and, indeed, the safety of emergency services.
"As much as I understand people's wish to push ahead and come to this conclusion or that conclusion, we just have to now let the investigators do their job."
Referring to helicopter accidents in the north east of Scotland, Mr Carmichael said: "Sadly we do see incidents involving helicopters from time to time."
Reviews of helicopter safety is "a job that should never stop", he said.
"But as the Deputy Prime Minister says, to try and draw too many lessons at this stage from one incident and try and apply them to other incidents is not perhaps the most sensible way to proceed."
Mr Clegg continued with his praise for Glasgow's people and emergency service workers.
"The thing that has really shone through to me is the extraordinary spontaneous manner in which everybody worked together on Friday night and in the following days," he said.
"You can try and prepare for emergencies like this as much as you like, but the greatest ingredient for an effective response is the community spirit we have seen here.
"A city which has had its fair share of divisions over time has actually come together in a remarkable way. That has shone through to the rest of the country, which is one of the many reasons why I wanted to pay this visit and come here today."
Commenting on his visit to the crash site, Mr Clegg said: "A hole has just been punched from the top but on the ground floor you can't see very much. I think what is obvious is that many other buildings would have collapsed under the weight of the impact."
The Deputy Prime Minister also met members of the ambulance service and police who worked with the officers and pilot killed in the crash.
"They are completely shell shocked and very distressed," he said.
"These weren't just colleagues, they were friends and human beings who they had got to know very well over the years."