Here are some links to places where you can search for electronic parts.

Please add sources as you find them!

Online Sources

DigiKey Corporation     http://www.digikey.com/

Sparkfun Electronics     http://www.sparkfun.com/

Evil Mad Science          http://evilmadscience.com/

Jameco Electronics     http://www.jameco.com

Adafruit                    http://www.adafruit.com/

Local Sources

Microcenter     http://www.microcenter.com/search/search_results.phtml?N=4294939904

RadioShack     http://www.radioshack.com/home/index.jsp?cmpid=loc3

You Do It Electronics      http://youdoitelectronics.com/

Solar Sources