If you have Mac OS X, and have ever opened the terminal window and thought “Um... yeah... what next?” I have good news. Mary Norbury-Glaser has created a step-by-step tutorial on using the Tiger Terminal. It even starts out with where to find the terminal window.
The article is pretty long (the first of five installments is three pages!), but it is very step-by-step. It does get into some stuff that she says can damage your system if you run the wrong commands, so use with caution. You'll also need administrative privileges on your Mac.
So, have fun getting your hands dirty in Terminal.