Kontakt Related

http://dummyworld.net/programs/
http://www.nilsliberg.se/ksp/scripts/tutorial/ 

http://www.mcgee-flutes.com/flutemic.html (connecting electrets)

Noise Reduction
http://www.stillwellaudio.com/?page_id=32
http://www.duystore.com/com/silence.html (ouch)
Izotope RX


Sound Libraries

http://www.boomlibrary.com

Headphone Amp Project

Nothing to do with the arduino but I'm fililng it there under all the bits and bobs.

Drive ICs
http://www.nxp.com/documents/data_sheet/TDA1308.pdf

Medieval related topics

http://www.trouvere.co.uk/
http://www.piva.org.uk/index.html 

Celtic Music:
O son Do Ar


Recorders:
http://www.aswltd.com/adultmet.htm

Places to buy stuff

UK
http://www.technobotsonline.com/
http://www.skpang.co.uk/catalog/
http://proto-pic.co.uk/
http://www.hobbytronics.co.uk/ <- Pololu imu
http://www.coolcomponents.co.uk/catalog/
http://www.active-robots.com/

Big ones:
http://www.pololu.com
http://www.sparkfun.com