In my research, I came across this site:

    http://www.learntcpip.com

which has several streaming media presentations on various pertinent
subjects, all with their own domain, as follows:

http://www.LearntoSubnet.com Lecture Series
"A Free, Lecture-based Educational Course on IP Addressing and Subnetting."

http://www.HowtheOSIModelWorks.com
"A  Free, Lecture-Based Presentation on How the OSI Model Works"

http://www.HowTCPIPWorks.com Lecture Series
"A Lecture-Based Presentation on How TCP/IP Networking Works!"

http://www.HowTheInternetRuns.com
"A Free, Lecture-Based Presentation on How the Networks of the World
Interconnect to Create the Internet!"

http://www.HowDNSWorks.com
"A Lecture-Based Presentation on How the Domain Naming System Works!"

I didn't go through them all, but what I did surf through was very, very
good.  Essentially, they are slide shows with streaming audio.

Problem:  They are in Windows Media Player's .asx format.  I have no idea
what, under Linux, might play them.

-Linda