Vintage microphone stuff – Good service and very good prices:
http://www.vintage-microphones.de

Good service. Cheap as well as expensive parts. Sifam, Lundahl and Pro Audio.
Components: http://www.canford.co.uk

Everything in electronics, good service and good prices.
Components: http://www.farnell.com

Lots of things for audio devices:
Components: http://www.musikding.de

Most common stuff. Excellent service and very good prices.
Components: http://www.el-supply.dk

Lots of things for audio devices:
Tubes: http://www.pyndtshop.dk