Some of my own (and others') favorite parts suppliers:

http://www.danssmallpartsandkits.net/

http://www.surplussales.com/

http://www.electronicsurplus.com/

http://www.circuitspecialists.com/

http://www.apexelectronic.com/

http://www.allelectronics.com/?iorb=4764

http://www.kitsandparts.com/

http://www.palomar-engineers.com/


Made this a sticky - anyone wishing to add to the list, please do so!

This could be a valuable resource for builders! <edit by ad4mg>