Bah, I posted a really long message, then got "No thread specified. If you followed a valid link, please notify the webmaster" and it wasn't in my cache
Here's a shorter version. Sorry it doesn't provide as much information.
I think a couple Mac magazines have posted "How To" guides for the Terminal in OS X. Mac Addict comes to mind, sorry, no links.
Navigation is usually the first things taught (besides learning that the "man" command is used for help... it's short for "manual").
You can use pine for reading e-mail in the terminal. Doesn't come with OS X though, requires a quick d/l, maybe a compile. gcc is a compiler that comes with OS X (developer tools).
You can telnet and ssh into a remote computer from the terminal. ssh is more secure, if the computer is setup for it. If you turn on "Allow remote login" in the System Preferences it sets up your computer so it can be accessed with ssh. There's ftp support of course too.
Cheers,
Dak