A bit of Freedom of Information jiggery pokery has got the records into the public domain two years early and you can look up specific people or see who lived in your house in the Edwardian era. (For example, your 'umble correspondent is currently sat in the former home of a cellarman's family, who had the mother-in-law over for a visit.) Or you can look up celebs: David Beckham's great-great grandfather was a Walworth “scavenger”, Kate Moss's great-grandmother was in the lower end of the fashion trade as a mantle maker and Amy Winehouse hails from Russian immigrant stock.
The census also proves that the more things change, the more they stay the same. One mother listed her occupation as “slave to family” and someone else wrote down their Persian cat. Feminists will get a swell of pride from witnessing a lot of Suffragette dissent.
If you want to get into any real detail you have to buy credits (cheapest package is £6.95) and, remembering the almighty crash when the 1901 census went online, the National Archives assure us their servers are stable. We thoroughly recommend having a poke around as you never know what you'll turn up. History: not just for geeks.