This site has scanned images of old maps for England, Wales and Scotland arranged by county.
http://freepages.genealogy.rootsweb.ancestry.com/~genmaps
This website is a portal for digitised maps from around the world including Australia. Collections include the David Rumsey Historical Map Collection, the British Library, the National Library of Scotland and many more. The results list gives the title of the map, date and scale and once a map is selected it is zoomable so you can see the detail.
http://www.oldmapsonline.org
The National Library of Scotland has made freely available historic maps of Scotland, England and Wales which are copyright free and can be used on websites etc.
http://geo.nls.uk/maps/api
Using Google Maps you can pinpoint locations around the world and see map and satellite views. Street View, often showing photographs of individual houses, is also available for large parts of Australia, the UK, the USA, Japan and some parts of Europe.
http://maps.google.com.au/maps
Interactive maps of England and some interactive coverage of Great Britain. Includes an overlay for administrative districts.
http://www.magic.gov.uk
View maps of places in England, Scotland and Wales mostly from the 19th and early 20th century.
http://www.old-maps.co.uk
Information about life in Britain taken from census data. Various themes are explored such as Population, Life and Death, Industry, Work and Poverty etc. There are also descriptions of places from travel writers and gazetteers as well as a collection of historical maps.
http://www.visionofbritain.org.uk/index.jsp
