Google has just removed the wait to receive a Google Analytics account. Now anyone with a website can instantly create one for free by simply by visiting google.com/analytics or by clicking on the “Analytics” tab within AdWords. After you create an account, read the Installation Guide to get it set up quickly and correctly.
In other words, the more you take action based on web analytics data, the better the Internet becomes. That’s the underlying philosophy of the Analytics team shares.
From – Google’s blog
U can use Analytics with sites like blogspot.. but not with WordPress as it already have Analytics code integrated to it (Blog Stat).
Google Analytics tells you everything you want to know about how your visitors found you and how they interact with your site. You’ll be able to focus your marketing resources on campaigns and initiatives that deliver ROI, and improve your site to convert more visitors.