Zoopla

Zoopla aims to be the definitive data resource for the real estate market in the UK. Covering all 27m homes, Zoopla's data sources include owners and agents who upload data enhancing the value of the database as a whole.
The Zoopla site is a searchable directory of UK residential properties, created as a mashup of Royal Mail's database, the UK HM Land Registry's data on property transactions, Google maps, Microsoft Birds eye view, and other data sources. The data is then presented in a read-write format, so that user generated content can "fill in the gaps".

Zoopla has started by providing free value estimates and sold prices on homes, allowing sellers and agents to list homes for sale and letting all users edit information and upload photos.

Zoopla's value estimates are calculated using a proprietary algorithm that been developed by analysing millions of data points relating to property sales and home characteristics throughout the UK. The algorithm works by comparing relationships between home prices, economic trends and property characteristics in given geographic areas.

Byteplay

Byteplay's flagship product, DotHomes is a Real Estate search engine.
DotHomes allows home seekers across the US, UK and South Africa to search over thousands of real estate Websites from one place. Underlying DotHomes' search mechanism is a Machine learning data-mining technology, which automatically finds property listings on listing broker / agent Websites, and extracts relevant information. This allows for extremely rapid scaling up of coverage, whilst still getting data directly from source Websites (as opposed to getting data from smaller aggregators).

DotHomes employs an advertising business model. It does not charge real estate listing brokers to have their property listings appear in the DotHomes search index. Instead it provides ancillary real estate services with an opportunity to advertise alongside the free "organic" search results.