There are many interesting websites for those interested in history. Below are some of the best ones for research in the UK, together with a selection of my personal favourites.
GENUKI - This comprehensive site contains lots of information about all parts of the UK and gives links to further resources.
The National Archives - I have spent many happy hours in the
treasure trove that is the National Archives at Kew. Many resources
and services are now available on line
General Register Office - This site contains lots of information about civil registration in England and Wales and is where you can order copies of certificates.
Old Maps - enables you to see a 19th century map of anywhere in the UK. It is really useful for checking the geography of the area where your ancestors lived, this can be particularly important to help interpret census information.
WW1 Battlefields and research - When researching the life of Chris Cox, I visited the places where he had been in action. The War Research Society helped me find the right places and looked after me while I was there. They are an excellent company and if you want to go to a battlefield or visit the resting place of an ancestor involved in war (anywhere, not just France) these are the people to go with.
Commonwealth War Graves Commission - information about the invaluable work of the Commission and access to their searchable database of men and women killed during First and Second World Wars.
WW1 Roll of Honour - a wonderful site dedicated to remembering those listed on War Memorials in the UK.
Find My Past -this subscription site gives access to many indexes, census records and other sources of interest to family historians. It is easy to use and good value for money.