Sources for Materials, organized by continent/location
global
ebay
Online auction site
website: http://www.ebay.com, http://www.ebay.de
you can get just about anything on ebay
sometimes even at good prices
Europe
Electronics
Conrad Electronic
website: http://www.conrad.com
"the pharmacy", biggest choice of stuff
often expensive
has subsidaries in many european countries
has stores in some bigger cities
ELFA
website: http://www.elfa.se
Not as much stuff as Conrad has, but still quite lots, ships internationally at least inside Europe.
Pollin Electronic, Germany
website: http://www.pollin.de
mostly suplus products
all kinds of stuff
Reichelt Elektronik, Germany (TIP!)
website: http://www.reichelt.de
good prices (often 50% compared to Conrad)
quick delivery
Velleman, Belgium
website: http://www.velleman.be
Plastics
Plexiglas(tm)/acrylic (PMMA), Polycarbonate/Lexan(tm)/Makrolon(tm) (PC) and/or Polystyrol (PS) can be found at some Home Improvement Stores.
BrettMartin sells "Foamalux". These are PVC foam sheets. http://www.brettmartin.com/semifinished/foamalux/foamalux.aspx
Mechanics
UK: Plastic gears: http://www.mutr.co.uk/prodDetail.aspx?prodID=781
Germany/UK/France: Springs: http://www.federnshop.com/
North America
Electronics
Digikey
website: http://www.digikey.com
download the huge PDF catalog (or use the website search), they have everything under the sun..
Mouser
website: http://www.mouser.com
same thing: nice PDF catalog & search, lots and lots of stuff..
Plastics
Craftics, Inc. Tools and Accessories for Working with Plastic http://www.craftics.com/index.cfm
Mechanics
Australia & New Zealand
Electronics
Altronics
website: http://www.altronics.com.au
Sells a quadrature rotary encoder
Oatley Electronics
Variety of surplus mechanics, stepper motors and electronic components.