Listed below are the some of my favourite links:

http://www.coneguitar.comSite of Michael Cone, influential American guitar maker.
http://www.luth.orgGuild of American Luthiers, lots of links to makers, suppliers, dealers.
http://www.guitarnation.comShowcase of international guitar makers.
http://www.kentguitarclassics.comSite of Miles Roberts, dealer with strong selection and no-pressure sales method.
http://www.saitenkatalog.deGood selection of strings at very low prices.
http://www.granary-guitars.comOne of the finest classical and flamenco guitar collections anywhere and all playable, if you ask nicely. some of the finest hand made instruments in the UK.
http://www.meghnaint.comManufacturer and supplier of top grade stringed musical instrument parts for violins, violas, cellos and double basses in ebony, rosewood and boxwood.
http://www.headwaymusicaudio.comHome of excellent pickups for classical and flamenco guitars.
http://www.customguitarboutique.comOffers a large range of hand built-instruments - classical, flamenco, acoustic and steel string - from top quality makers.
http://www.estiloflamenco.comFrancisco Antonio is a great flamenco player and teacher.

If you are a maker, player or materials supplier and would like to be added to this list, contact me with details of your site and a description of what you do.