I would say probably the best forum on the web for WW1 and more, but there is no probably about it. Its size of membership and the enclosed knowledge because of that make this stop number one when you have a question about WW1 or surrounding topics. An addictive forum that will get hold of you. Sign up and become one of the Pals of Chris Baker's fantastic community.
A fantastic resource for anyone wishing to gain information in regard to the Great War. Full of tatical analysis, personel accounts and general narrative of World War One. This should be your first stop for information. This is the mother site to the Great War Forum.
A new and engrossing site that has no real connection to 21st Division but a classic example of what a dedicated Website can be about. The Battle of the Somme was fought in the main by 4th Army of the BEF. This tells the story of the battle of Gommecourt which was the diversionary action conducted by LT-General Sir T D 'O Snow's VII Corps of Allenby's Third Army.
This is not just a Museum of great content but it houses numerous resources. From Great War photgraphs to documents and a library of Great War books. Viewing details can be found on the site.
Also known to many as the PRO (Public Records Office) Those who refer to it as this will be seasoned campaigners and frequent visitors. An absorbing and mind blowing record facility of War Diaries, soldiers records (limited number) Officer records, maps, Medal rolls and much much more. You can search on line, download some records on line and also order up records for viewing before you go. The use of computers and cameras is also allowed so long as permission has been granted.
The official site of the organisation that as its 'motto' says,
The Western Front Association was formed with the aim of furthering interest in the period 1914-1918, to perpetuate the memory, courage and comradeship of all those who served their countries in France and Flanders and their own countries during The Great War. It does not seek to justify or glorify war. It is not a re-enactment society, nor is it commercially motivated. It is entirely non-political. The object of The Association is to educate the public in the history of The Great War with particular reference to the Western Front. Applications for membership are welcomed from anyone with a like mind.
Firepower: Royal Artillery Museum
Home of the Royal Artillery museum, lots of facts and displays.
Another cracking site on the Great War, with numerous articles from knowledgable contributers from around the world. Also the 'home' of Tom Morgan Military Books, formerly Ray Westlake Military Books. A massive selection of books covering all aspects of the Great War.
A great resource holding numerous Great War officers and personalilities papers and other items.
Canadian Expeditionary Force Study Group
A forum for in the main a study, as the title says, of the Canadian Expeditionary Force. It's first units touched the shores of France in late 1914 as part of 27th Division (Princess Patricia's Canadain Light Infantry) , by the wars end they would have an independent Corps commanded by one of the best Corps commanders of the war, Lt-General Currie and a reputation second to none.
Join this group, to learn or contribute, the choice is yours but enjoy.
The Centre for First World War Studies
The centre is based at Birmingham University. More often than not the friends and members meet twice a month on a tuesday evening to hear emminet speakers talk on the Great War and other related topics. The resources of the centre can be a major benefit to its friends and members, with the knowledge of the centre being vast. With the likes of Dr John Bourne, founder of the centre and the appointment recently of Prof Gary Sheffield as the chair of the centre, the focus is to strive to be the first stop calling centre of advice and academic advancement, with its Great War degree courses well under way. The centre also has day seminars two or three times a year.
Old Front Line Battlefields of WW1
A very informative site, packed full of details from someone you would expect to know there stuff. Paul Reed is a prominent figure in Great War circles and has written widely on the subject. Through his company he also 'educates' others with battlefield trips and has also appeared on the television. You can take that to mean that he knows what he is talking about and that the site will be well researched and accurate. A general site that gives information on different areas of the war, you can get a good over view of world war one.
3rd Battalion The Monmouthshire Regiment
A cracking site, dedecated to a battalion of the Monmouthshire regiment, showing the life through personel experiences and the battalion war diary. It also showes some of the actions it was involved in and the men who fought in it. The divisional formations it served under are also discussed. Whislt not a connection to 21st division, certainly a good site to look around and see how a battlion fought during the war.
A new site about another division of the Kitchener Army. At time of this writing still in its infancy but shows signs of building into a very credible on line history of another Great War division. The 17th Northern division had much in common with 21st and their paths crossed on occasions, especially at Fricourt where they worked hand in hand as 50th brigade was seconded to 21st divisions attack around this village. It suffered great casualties, with the 10th battalion West Yorkshire regiment suffering the highest single day casualties of the war, 22 officers and 688 other ranks being killed, wounded or missing. With only one officer remaining alive at the end of the 1st July, even he was wounded.
This site specialises in Battlefield walking tours. Run by Julian Whippy and Clive Harris, both who are members of the WFA. Take a look at thier web page it may interest you. I have not used them myself but they do come well recommneded and with excellent background qualifications , including the Guild of Battlefield guides.
A small site of a personal journey to trace the actions of a relative. As the site begins it says " What follows describes a walk that may be taken to commemorate the action of the 110th (Leicestershire) brigade between the 14th and 17th July 1916."
Nice little site good pictures of the surrounding area in modern form.