I use iTunes 4.6.0.15 on Windows XP, and I'm on a college network. 
How can I see who's connected to my shared music library (streaming my
music)?  I'm interested in seeing their IP addresses and/or the names
of their shared libraries.  If you can point me to some third party
software that does this, that will also be appreciated.

I wondered this myself. I haven't found any software to do this automatically.
You can see the names of computers connected to your computer.

Open a command prompt (or go to Start > Run and type 'cmd')
Then run "netstat -a".
Look for lines that are connected to port 3689.
For instance:

TCP    you.college.edu:3689            bob.college.edu:51014  ESTABLISHED
This means that the computer named "bob" is connected to yours.

TCP    you.college.edu:2029            john.college.edu:3689  ESTABLISHED
This means that you are connected to the computer named "john".

Depending on how your college is set up, this may not be so useful.
You might get addresses like "dhcp812794.college.edu", if everyone
uses DHCP.