I plan on teaching in Northern British Columbia and electronics parts and resources are hard to come by.
This is a link to some electronics kits, the kits come with all the pieces to build what you need.
http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20160110100622&SearchText=guitar+pedal+kits
It is a great idea to order kits because all the parts come with it and it ships to the location.
I picked electric guitar effect pedals because playing guitar is a hobby of mine and manipulating sound is always fun.
http://www.generalguitargadgets.com/
This is another site that is great. It has schematics and kits.
This next site I plan on using with the students to teach them about sound theory and show what happens to sound.
http://www.falstad.com/circuit/
Any circuit can be made and you can see what is happening.