The National Library of Wales has quite a lot of online family history content. Select Family History - Search Archival Databases for online indexes to marriage licences 1616-1837, court records 1730-1830, pre-1858 wills and more. Select Digital Mirror for digitised content including maps.
http://www.llgc.org.uk/index.php
View maps of places in England, Scotland and Wales mostly from the 19th and early 20th century.
http://www.old-maps.co.uk
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
This site has scanned images of old maps for England, Wales and Scotland arranged by county.
http://freepages.genealogy.rootsweb.ancestry.com/~genmaps
The National Library of Scotland has digitised the Ordnance Survey's six-inch to the mile maps for England and Wales. This is the most detailed topographical mapping covering all of England and Wales from the 1840s to the 1950s. Maps are zoomable and the easiest way to find a specific place is by going to the Find by Place tab.
http://maps.nls.uk/os/6inch-england-and-wales/index.html
This is a beta site with online content drawn from archives and other sources around Wales. Users are also encouraged to add their own digital content including family trees.
http://www.peoplescollectionwales.co.uk
