Tunnel diodes are a bit rare these days, but still have uses in special applications including extremely high frequency oscillators, etc. They were commonly used in microwave circuits, oscilloscope trigger circuits, and other applications. This video reviews the basics of tunnel diodes, including the basic properties and simple applications. I refer to these as the "bucking bronco" of diodes because of the IV curve that jumps around, and the fact that these diode will jump into wild oscillation if you just look at them funny!
There is a lot of information on tunnel diodes on the web. Here are just a few links with a wealth of information:
A ton of great information and links to a lot of tunnel diode manuals and papers can be found on this page:
http://w140.com/tekwiki/wiki/Tunnel_diodes
In particular, check out the links to some of the tunnel diode manuals near the bottom of the page:
http://w140.com/tekwiki/wiki/Tunnel_diodes#Textbooks_and_references
This paper has a ton of tunnel diode info:
http://www.physics.clarku.edu/~tcoffey/ThesisStorage/chp4.pdf
Of course, there is a wikipedia page with good info and links:
https://en.wikipedia.org/wiki/Tunnel_diode
And, here is a copy of the notes used during the video:
http://www.qsl.net/w2aew/youtube/tunneldiodes.pdf