Checking the price a friend or neighbour has paid for a property is a cinch, thanks to Land Registry data available free online (at www.LandReg.gov.uk and Rightmove.co.uk). Now a new website takes this a step farther, offering estimated current values for 26 million homes. In addition, property owners can “claim” their listing, adding information on things such as the number of bedrooms to boost the estimate.

The free site, Zoopla.co.uk, serves as more than a snooper's paradise, however. Homeowners or agents can advertise a home for sale and users can place non-binding “TemptMe!” offers on all properties - even those not on sale. They can also post questions on each home or area page, such as “has your kitchen been updated?”, or “what are the shops and pubs like in Chipping Norton?”

Alex Chesterman, the site's founder, says that the “community website” covers all homes listed by Royal Mail. “Most users start by looking up their own home, then check on their friends. It can get addictive,” he says.

Mr Chesterman explains that value estimates are based on the last sale price, where available, plus local and wider pricing trends. I registered free to check estimates for my home and others I know. A search of my London postcode finds instant estimates for only a handful of properties - those sold since the Land Registry data cut-off in April 2000. To view estimates for the others, I must enter details of tenure, number of bedrooms and so on.

Details submitted in this way are published on the site. Reluctant to submit half-remembered details of neighbours' properties, I enter data for my home and am disappointed to see a “value” well below expectations. I give the estimate a two-star rating and am invited to enter feedback.

Mr Chesterman explains that all further information submitted in feedback is considered by analysts and factored in - although this can take weeks. “There are lots of things that can't be entered on the form,” he says. “We have had people tell us that their shed has a power supply or their garden has wheelchair access, for instance.”

One of the site's key features is its TemptMe! function. This works two ways. Homeowners can list a price that would tempt them to sell and potential buyers can post a non-binding offer on any home in the hope that the owner will come across it.

Anyone thinking of buying a property listed on the site should be aware that Zoopla! is not an estate agent and the buyer is responsible for checking and confirming the accuracy of all details, instructing a surveyor and seeking legal advice. Those considering selling their home online should read Times Money's guide to selling without an estate agent at www.timesonline.co.uk/mortgage.

CASE STUDY: 'Make me an offer I can't refuse'

Melissa Greenston logged on to Zoopla! after a friend's recommendation to check the estimate for her four-bedroom 1920s semi-detached house in Mill Hill, North London: “It was about right at £630,000,” she says. “We have done work to the interor, which could up that by about £50,000, so I explained that in the feedback.”

Mrs Greenston, who runs a head-hunting company and is married with two children, has no plans to move but entered a TemptMe! figure of £850,000. “The function is excellent because it addresses that dinner party conversation you always have: how much would make you sell?”

She admits that the site's main attraction for her, however, comes in looking up friends and relatives. “It sounds bad, but it's fascinating and

you get hooked,” she says. “If we are honest, we all want to know what our friend or mother-in-law's house is worth. I've had a couple of surprises.”