Places to buy parts:

Electronic Parts

• http://www.sparkfun.com/ All kinds of fun stuff + slightly cheaper Arduino clones.
• http://elektronik-lavpris.dk/
• http://www.smartprj.com/ Original Arduino
• http://robot-electronics.co.uk/acatalog/Ultrasonic_Rangers.html Ultrasonic rangers and more

• http://truss.dk Dansk Disco Support - reasonable prices on lamps, DMX dimmer packs etc.
• http://eskildsen.dk reasonable prices on synths, LED lamps etc.

Ultrasound sensors

• http://www.parallax.com/
• http://www.trossenrobotics.com

Servoes etc

• http://www.rc-netbutik.dk/
• http://www.servoshop.co.uk/
• http://www.holte-modelhobby.dk/