http://home.earthlink.net/%7Ewb5rex/xtalman/detectors.html

Another thing to use for a detector was an old fashioned double edge razor blade, in particular, the (Gilette?) "blue blade". Touching the tip of the safety pin (or pencil lead) to the blue area, right next to the silver area would supposedly act as a detector. Those old blades no longer exist.

http://www.geocities.com/safetyrazors/blades/DEBladePage.htm

Makes you wonder who first got the idea... "Hey, let's take a razor blade and a pencil lead and..."

You think I jest?

http://bizarrelabs.com/foxhole6.htm (as a kid I had the book on this page "All About Radio and Television")

http://www.bizarrelabs.com/foxhole8.htm

And you had to have an oatmeal box to wind your coil... hah!

Here's the classic Quaker Oats crystal radio.

This site has lots of links, kits, plans, etc:

http://www.midnightscience.com/

http://www.midnightscience.com/catalog5.html

You can literally build this loop antenna, add an earplug and diode across the variable capacitor connections, and make a crystal radio from it:

http://www.mtmscientific.com/loop.html

Here is the correct diode, a 1N34A. You used to be able to buy a bag of these at Radio Shack for a buck or so.

http://www.mtmscientific.com/diodes.html

Just google "crystal radio" and you can find plenty of sites.

This one, Dave Schmarder's site, has both AM loop antennas and crystal radios:

http://www.schmarder.com/radios/misc-stuff/loops.htm

http://www.schmarder.com/radios/crystal/30.htm

Dave's crystal radios are very sophisticated. In fact, they are the most sophisticated crystal sets I have ever seen. Amazing!

http://www.schmarder.com/radios/index.htm