Various county family history societies have their own web sites, such as Bedfordshire Family History Society, which have links to societies for other counties. The Federation of Family History Societies site has now joined with the findmypast site to provide pay-per-view databases on-line. The England GenWeb Project is a site to help researchers find local resources and reference information. The site has links to sites for various counties, e.g. Bedfordshire Genealogy. The Roll of Honour link from that site gives details of a large number of men & women listed on War Memorials & in Rolls of Honour in Britain and abroad.
The Commonwealth War Graves Commission site has search facilities for basic commemorative information about men and women of the Commonwealth forces who died during the two world wars. It also lists civilians who died during the Second World War as a result of enemy action.The Charles Booth Online Archive is a survey into life & labour in London dating from 1886 to 1903. There are searchable poverty maps & original survey notebooks, plus digitised police notebooks. The British Library Newspaper Archive has facilities to search through its collections of newspapers, magazines, documents & books. The Society of Genealogists site has some material on-line such as the list of Parish Register copies held in its library, the Subject & Surname Index from its magazine & various information leaflets. If you think some of your ancestors may have been a Red Cross worker or volunteer during WW1 then the Red Cross web site may have some more information. The records are searchable by name, location, etc.
If you ever find documents giving details of an ancestor's wealth, you can relate it to present values by using the Current Value of Old Money site.
Although not directly connected to family trees, the Britain From Above web site has aerial shots of Britain dating from 1919 to 1953 that may show where some of your ancestors used to live. In order to be able to zoom in on the images and add pin-marker comments you have to create a login, but it's all free and you don't get nagging emails or advert spam from the site.
Another good site for old photographs is the HistoryPin web site. If you create a login then you can add comments to photos already in the collection or add your own photos to it.
The Historic England web site (used to be called English Heritage) also has old photos that may relate to your ancestors. The site is accessible now but as it is still under development the content and layout may change in the future.
In tracing my great great uncle William Gibbs who emigrated to America in 1866, I came across the Chicago Tribune Archive site, the U.S. Archives site and the Internet Archive site that proved very useful.
If you take photos on a smart phone of anything related to your family it is worth enabling the GPS location option in your camera settings so that you can use the grid reference in the photo's meta data at a later date to locate where you took the photo. Details of how to do this are shown on this page.
Lilly Graham reminded me of the web-site that has lots of links regarding immigrants entering America via Ellis Island in New York.
Girl scout Colleen and assistant scout troop leader Corrine Hayes sent me the link to the Parker Waichman web-site which has more history and links relative to Ellis Island. This gateway into America was operational from 1892 to 1954, so if you have ancestors that emigrated between 1820 to 1892, the Castle Garden records would be more useful. Various family history web sites have information about these records that can be found by searching for "Castle Garden immigration".
Stacey Martin sent a link to a web site that has useful tips found by student Anna & her mother. This site is unusual as it also has tips for adopted individuals.
If you have any ancestors that may have emigrated by ship, passenger lists also have useful information. Thanks to one of Anita Gianakas' students, Amanda Phillips, in Knox County, Maine, for sending this link with useful tips regarding ship passenger lists.
The house records of where your ancestors lived can also provide useful information. Amanda sent this link which may be useful.
Surprisingly, the Crossword Solver web site also has some useful links to genealogy related web sites. Mitchell Cruickshank sent me the link which may be useful.
Stephen Mash sent a link to a web site that has useful tips and links to other family tree related web sites.
Although the Word Tips web site is mainly aimed at teaching history, it does have some interesting facts that cover events our ancestors have lived through. Thanks to Zane Robertson for sending me the link.
If you have European roots, Joe Laurel's link may be useful as it has links to other resources in European contries.
If your children are interested in their family history, then a web page link supplied by Melissa, who is a student at the North Mountain Institute, may be helpful.