I have been using Google Analytics for a while to be nosey on my class site and the Digital Footprints site. ( links in the side bar ).
You can have as many sites to track that you like, as you can see here on the analytics dashboard, I now have 3.
It is easy to set up, you just have to put a couple of pieces of key information in specific places.
You start in the manage site section on your site, and part way down you will see this box to tick. It will not have a code in at that point, click on the part that says "learn more"
This take you to this, where you need to click the second option, for configuring.
This configuring page takes you through all the steps you need to do to set up your site.
You need 2 things, the code to put in the box and some html that you put onto the pages you want it to track.
I only did this the other day for the How To site, and I am already surprised by the traffic that has come through the site. It gives the information in nice handy little graphs, and breaks it down into where they are from, browsers used and all sorts of other stuff that I really don't care about, BUT, you can never have too much information!!!....