Archery websites of all known Kingdoms:
The Midrealm Archery Marshal's Handbook is on this page - it's listed as "Missile Weapons Marshal's Handbook", and is available in either .pdf or .doc formats.
The Midrealm Archer General's website - Midrealm archery information, calendar, regions and deputies, and many links.
The Greenwood Company of the Midrealm.
Some Important Events in the Fourteenth Century - this page has some good historical information, including a 15th century illustration of the Battle of Crecy, showing English archers using longbows, and French archers using crossbows.
The Society of Archer-Antiquaries - furthers the study of the development of the bow and arrow in all parts of the world from prehistoric times to the present day and also matters relating to the history of archery in general. They've also got a lot of really great articles about many aspects of archery.
Interested in Thumb Rings and other Mongol archery tools? Check out ATARN (Asian Traditional Archery Research Network).
Conquest Anglo-Norman Society - This group does serious reenactment of the Anglo-Norman period. There are some good photos of their archers, and a short article on crossbow construction.
Michael Drayton's Ballad of Agincourt
The legend of William Tell
Stefan's Florilegium (a collection of postings from various sources) has an entire section on archery
A collection of FAQs (frequently asked questions) from an archery newsgroup.
The Life of Ascham by Samuel Johnson. Roger Ascham is the author of Toxophilus, or the Schole or Partitions of Shooting. Published in 1544, it's a treatise on all aspects of contemporary archery at the time. He covers everything - equipment, shooting styles, mental attitude and more - sometimes in extreme detail. It's very practical in some sections, philosophical in others. It's an absolute gold mine about archery that is still relevant today, and it's about the only Medieval period book on the subject - the only one in English, anyway. If you're really interested in traditional and SCA archery, it's really worth tracking down a copy and reading it.
Information about the archery collection at the Manchester Museum, in the UK (includes information about the Simon Archery Foundation - if anyone knows their webpage address, please email me the link - thanks).
Some information and comments on Archery Laws in England regarding required practices
Oxford Archers - you have to check this out, if nothing else, than for the great effect when you put your mouse on the links on the main page.
No Frontiers Archery - cedar arrows, also bows (including longbows), used bows, books, and accessories.
Bitter Root Bow Co. - nice selection of longbows in a variety of different woods, including a short version for youth (a nice size for mounted archery too!). Also cedar arrows and some accessories. Very fast shipping.
Bowstick Archery - this is their 'arrowbuilder' page. Custom built arrows - choose your options and watch the arrow at the top change to match.
And, because so many archers seem to be interested in it, here's a link to the Gwyntarian Tunner's Guild, devoted to brewing and vintning.