A £26,000 bill for training Cabinet Office staff to have "difficult conversations" is among revelations of Whitehall spending since the election.
Details of about £80bn of spending on items over £25,000 have been published online as part of what ministers call their "transparency agenda".
The government said some revelations would be uncomfortable but taxpayers had a right to ask about expenditure.
But critics warn that the numbers are almost meaningless without context.
The government says publishing thousands of data entries - some 195,000 lines of data - allows developers, organisations and companies to "reuse and reinterpret" it.
People are being encouraged to pick through the enormous quantity of online information to spot waste and hold ministers to account.
Cheque for Charles
All spending of more than £25,000 made between May and September was published - in line with a pre-election commitment by the Conservatives - although some departments also published spending over £500.
Analysis of the data by the BBC shows Capita was the biggest private sector recipient of taxpayers' money - with £3.2bn out of £3.3bn going on teachers' pensions.
Prince Charles also got a cheque from the Ministry of Justice for £667,000 - rent for Dartmoor prison, which is on his land. He was also paid £677,000 by the Army for access to Dartmoor.
Among other private companies that receive large amounts of public money are the property company Trillium and technology giant Hewlett Packard, which have each received about £285m since the election.
Accountants KPMG and PricewaterhouseCoopers were each paid £22.5m for government contracts between May and September.
The government's car service also received payments totalling almost £1.5m from departments, including £123,000 from the Department of Energy and Climate Change for "ministerial support".
Among the smaller sums detailed was a payment of £1,000 from the Department for Business, Innovation and Skills to a company that sells jewel encrusted dog collars and pet fashion accessories to help it expand into the US.
In a video broadcast on the No 10 website, David Cameron said the publication of the information was a significant step forward.
"Just think about what this could mean," he said. "People will be able to look at millions of items of government spending, flagging up waste when they see it, and that scrutiny will act as a powerful straightjacket on spending, saving us a lot of money."
But BBC home editor Mark Easton said some data given to journalists before the public launch had later been removed from public view.
Pre-released figures seen by the BBC showed the Ministry of Justice paid eight people a total of £2.2m compensation for miscarriages of justice - among them two businessmen caught up in the Arms to Iraq scandal in the 1990s.
A Ministry of Justice spokesman said the information had been removed for data protection reasons.
Cabinet Office minister Francis Maude said: "The data isn't as good as it should be and not as good as it will be going forward. Certainly, a lot of the systems in place don't disclose, with anything like the precision that people are entitled to expect, what the money is being spent on."
It is the latest in a series of online publications of data. Last month the government published the salaries of thousands of civil servants, naming individuals earning more than £82,900 for the first time. And in June it published the Coins database of public spending data.
Mark Easton said it was part of the government's plan to abolish professional Whitehall scrutineers like the Audit Commission and replace them with an "army of armchair auditors".
The Audit Commission, the local government spending watchdog which is set to being abolished by the end of 2012, welcomed the release of the information but warned that bare figures did not provide the whole story.
"It will allow ordinary citizens to ask legitimate questions about spending, questions which will become an irritant to government departments, but I think a legitimate irritant, as citizens seek to find out what money was spent on," its chairman Michael O'Higgins said.
"And that's where I think the critical issue is - that what is being released is not in fact information, it is data. And data needs context to become information, and it is provision of that context that will be important."
Information Commissioner Christopher Graham said the development could mark "an exciting new chapter" in Freedom of Information.
"The government's transparency agenda presents a great opportunity to take information rights to the next level," he said.