The Aerogramme website which is dedicated to the study and enjoyment of world-wide Aerogrammes (Aerograms), Air Letter Sheets and the equivalent. It includes a number of military related exhibits as follows:

http://www.aerogramme.com

New Zealand POW Aerogrammes:
http://www.aerogramme.com/exhibits/nzpow/overview.html
POW Aerogrammes of Australia:
http://www.aerogramme.com/exhibits/auspow/overview.html
Southern Rhodesia Military Airletters:
http://www.aerogramme.com/exhibits/sorhodmals/overview.html
Military Aerogrammes of the World:
http://www.aerogramme.com/exhibits/wwmals/overview.html
South Africa's UN Korean Forces Airletters
http://aerogramme.com/exhibits/soafrunkorea/overview.html

Egypt Study Circle:

http://www.egyptstudycircle.org.uk

Far East Prisoners of War Mail:

http://www.fepowmail.com

Military Postal History Society:

http://www.militaryphs.org

Canadian Military Mail Study Group:
(part of The British North America Philatelic Society):

http://www.bnaps.org/index.htm

CMMSG Newsletters to 2002: 

http://bnatopics.org/hhlibrary/newsletters/n-mm.htm

A pictorial catalogue of First Day Covers and commemorative covers issued by, or related to, The Corps of Royal Engineers.

http://refdc.fatpumpkins.com

The collection depicts British Forces mail in Kenya during the Mau Mau period of 1950-59; the post-Mau Mau period through to independence in 1961 and up to about 1963. There are also a couple of later items from 1993/94.  A wide variety of covers and postmarks are shown, many with unit cachets.  Also a few RN covers with POSTAL FRANK / ROYAL NAVY / MOMBASA (two types) and RESIDENT NAVAL OFFICER / MOMBASA.

http://www.britains-smallwars.com/kenya/postalhistory_kenya/postalhistory.html

Naval Cover Museum

The Naval Cover Museum is a virtual museum that exists only on the Internet and was established in 2000 by Paul Bunter, a naval cover collector and member of the Universal Ship Cancellation Society (USCS).   He is Curator of the Museum.  The 'new' Museum has been set up as a Wiki.  The Museum collection consists of scanned images of naval covers or parts of naval covers and is accessed via several indices.  These indices allow quick access to (US Navy) naval covers associated with ships, naval installations, cachet makers, cachet categories and other miscellaneous categories; it is work-in-progress and new images will continue to be added at a steady rate.  This site provides a facinating insight into US Navy ships postmarks and is an invaluable reference site.

http://www.navalcovermuseum.org

Also view:

http://www.navalcovermuseum.org/uscs/postmarkmailer/

which provides details and listings on different types of postmark either by vessel or postmark type.

'Warcovers' offers for sale material covering the postal aspects of all wars & military actions worldwide from 1800 to date covering the Army, Navy, RFC & RAF.

http://www.warcovers.co.uk