Open Data is data (including but not limited to geographic data) that anyone can access, use or share - often released by big companies or governments. In the UK the
Open Data Institute (ODI) promotes open data.
The UK's Ordnance Survey (OS) have
OS OpenData - "a range of quality assured, regularly updated products that enable you to analyse your data, build interactive websites and create stunning visuals – and they're all free"
Open Data Nottingham has been created to support and facilitate Nottingham City Council's commitment to freeing up Nottingham's data - they want citizens to be able to use the data that is held within this site - free of charge in innovative ways to create websites, apps and mobile products which people find really useful.
They also have a page linking to
others who offer open data, such as British Geological Survey, English Heritage, and
MAGIC (the website providing geographic information about the natural environment from across government).
data.gov.uk is the UK's open data portal, and you can use this to search for data by theme, name, publisher (usually government department), map location etc. Departments publish through this portal, but they also make data available through other portals - eg
the Department for Environment Food & Rural Affairs (DEFRA) lists such portals on its data page.
As a result of the government's initiatives, most UK county (and other) councils have "Open Data" sections on their websites, which you can find using eg
this search. Some of this data is geographic, but usually not much is historic.
The specific example for my local council (
Cambridgeshire County Council) includes geographic datasets, in
KML and Shape file formats, for divisions such as wards, parishes and "super output areas" (whose boundaries do not change, giving stability over time). It also includes
My.Cambridgeshire, powered by
iShare from Astun Technology - where residents can see lots of data about their neighbourhood on maps. It also includes
Cambridgeshire Insight, which "is a shared research knowledge base for the Cambridgeshire and Peterborough area. It allows users an easy way to access and share information and research for deeper insights about their local area."
Note that The
Center for Open Data Enterprise(CODE) works "to improve the open data ecosystem in the U.S. and internationally."