Medieval illumination:

http://www.getty.edu/: Getty Museum

http://www.tempora-nostra.de/index_f_neu.shtml?manesse0-9: Codex Manesse.

http://prodigi.bl.uk/illcat/TourIntro1.asp: the British Library.

http://www.ville-avranches.fr/manuscrits/tourisme_manuscrits.htm: Avranche Library.

http://www.bnf.fr/: National French Library.

http://expositions.bnf.fr/phebus/manu/index.htm: Gaston Phebus Book of Hunting (in French).

www.abdn.ac.uk/bestiary/: Aberdeen Bestiary

http://www.jcsparks.com/painted/recipes.html: many formulas for the illumination in English.

www.gallery.euroweb.hu: many reproductions.

http://www.snake.net/people/paul/kells/ : Book of Kells Images

 

Calligraphy site:

Cynscribe The most incredible links page for calligraphers / book artists / lettering people you are likely to ever find.