There is a great bash/cmd-line article in this month’s redhat magazine that will be a great read for all you linux newbies out there. It touches on a number of essential commands. Stuff that you’ll use every day once you use them and learn their syntax.
I say after reading the article go spend some time practicing what you learned. Skip the looping stuff and hit the find and grep commands as your first task. Then take another look at the article and touch on the other commands covered there. You’ll probably find a number of uses for xargs, just like the article says.