GoogleAnalytics is a very cool free online tool for tracking site usage and access. It includes some very cool features like showing usage over time, tracking sources and showing where users are viewing your page from. It's very simple to set up in a traditional webpage, too, by just planting a little snippet of code at the bottom of your pages. It's also very easy to set up on a Blogger page.
First, log on to GoogleAnalytics and set up a new account for your blog. You'll receive tracking code that needs to be inserted into the HTML of your blog's pages. Fortunately, this is really easy thanks to Blogger using a HTML template for every page of your blog.
For those with HTML savvy or heavily modified layouts, you can do the same thing by just putting the tracking code at the bottom of your page's body. Then again, you probably already knew that.