British Military History Sites

http://www.britisharmedforces.org/ns/nat_history.htm
The above site includes information about the regiments and their deployment, badges, tanks, troopships, aircrafts, armour and weapons etc.

http://www.nationalarchives.gov.uk/
Digital images of wills (probate records), Cabinet Records, pictures, photographs and historical documents from the Public Record Office are available at http://www.nationalarchives.gov.uk/documentsonline/
This site also includes army, navy and air force personnels service records and war diaries etc.