Web building tools:

Coffeecup
To create and upload files I have used free HTML and FTP tools from Coffeecup.

Dealers:

eBay
A good place to find British WW2 items.
The Quartermaster Store
British WW2 items, also other nations and other periods.
Pegasus Militaria
Stephen Kiddle makes very fine reproductions of those hard to get items.
Sabre Sales
British WW2 items. Sober website does not properly reflect their assortment. Just send e-mail with what you are looking for.
Ian Skennerton
Author of books on British firearms, bayonets, ordnance stamps, Small Arms Identification Series and other key reference books. Everything you've always wanted to know, and more!
Naval & Military Press
Online bookstore with a massive catalogue.
Milweb dealers
Portal to a vast amount of dealers, arranged by category and name.
Western Antique Arms and Books
Excellent book dealer. This site is in Dutch!
Para Phenalia
Books, rations, homefront items and many other collectables.
Geoff Newman Militaria
Excellent source for British and Commonwealth insignia.

Fellow collectors:

Henri's collection page
Focal point of Henri's collection is British and American WW2 uniforms.
My Grandmother's Brothers in the First World War.
Lars Alfers' site on his relatives during WW1; and his collection.
British airborne living history Group
This site shows excellent pictures of personal kit, weapons, equipment etc.
The visual collector
David Gordon's website. You can purchase good reference books here; be sure to check out the links pages with information about airborne jeeps, trailers and much more!

History related:

250 (Airborne) Light Composite Company RASC at Arnhem
Philip Reinders' website about this little known unit.
The Pegasus Archive
An overview of WWII British airborne operations. Mark Hickman has done a great job here: roll of honour, unit histories, biographies and much more.
The Sten gun
Site about the various Sten gun models. For now in Danish, but an English version is under construction.
The Air Despatch Association of Great Britain.
Very informative site about the British air despatchers from WWII onwards.
Royal Artillery units in the Netherlands 1944-1945
A wealth of information about the various batteries in the Netherlands; guns and ammunition, unit histories and more.
Karkee Web
Great website run by John Thorne about webbing, accoutrements and personal equipment as worn by British and Commonwealth nations.

Recommended forums:

Tommy Talk
A Dutch collectors forum.
British and Commonwealth section of the WA forum
British and Commonwealth military badge forum