This week's book giveaway is in the OCAJP forum. We're giving away four copies of Programmer's Guide to Java SE 8 Oracle Certified Associate (OCA) and have Khalid A Mughal & Rolf W Rasmussen on-line! See this thread for details.
Sure. If you are using an open operating system like Linux, you can find out a great deal of information via the /proc filesystem, including the status of network devices and traffic figures.
If you are using a closed operating system like Windows, well, I guess there's always the Windows API and JNI.