If you're interested in seeing how many visitors you get on your blog, where your visitors come from, how they found you and where they live in the world, then a great tool is Statcounter.
It's really easy to install too. Just follow the link above, register, follow the simple instructions, then sit back and relax while it does all the hard work for you. Even better, it's free to install and use.
You can see how people find you to see if you're targeting the right audience for your blog.
You can even label the IP address to see how many times people return. A bit like 'Big Brother' I suppose HAHA!!