For years UK based web-developers have been striving to find workarounds on behalf of clients with restricted budgets requiring postcode driven web applications. The Royal Mail do supply the data, but it comes with a huge price tag.
The workaround is usually to stick to town or county level geo-positioning. Various alternatives do exist such as pay-per-search services where postcode data is accessed via a subscription service with clients paying up-front for bulk search credits, but this too can get expensive. The open-source postcode project Free The Postcode was a fantastic idea and a very bold attempt but never quite got enough data to make it worthwhile for commercial use.
The good news is that as of April 2010 the British Government is going to be making OS data including post codes available for free! We don't know exactly what format the data is going to be available in but it is likely to be a simple database assigning each post code to geographical co-ordinates. Watch this space !
In the meantime there's been quite a bit of buzz in the news surrounding the governments other data liberating service. Take a look at http://data.gov.uk and you'll find a slick website reminiscent of some of the leading web 2.0 developer portals. Web-developers can now access a myriad of data sources for use in web applications and the project has been overlooked by none other than Sir Tim Berners-Lee, the inventor of the world wide web. The data seems to cover everything from the totally useless to some more interesting data with obvious practical uses, some recent examples of developer applications when I visited the site today included an accounts application that allows you to search and store company data from Company House and an application which provides an interactive map of potholes in the UK's roads !?
Whilst I'm going to take a closer look at the data.gov.uk website and perhaps have a play around with some of my own mash-up ideas, what I'm really looking forward to is getting my hands on the postcode data in a few months time!