Google Analytics is invaluable for measuring traffic to your site, checking your keywords, and watching interaction. They introduced a few new tools today which will make it even better.
Content Experiments - this replaces the old Website Optimizer. It lets you do A/B splits (test two versions of a landing page for example), or test something on every X number of visitors to your site. You can also choose what percentage of your audience gets to see it (so, you can test the red button vs. the blue button on a small portion of your visitors, and then let everyone see the version that worked best). Here’s a video of how it works.
Social Reports - tracks back shares of your post on social networks (look for it under Social Sources and then Activity Stream). It shows shares from Rediit, Disqus, Delicious, Google+ and other social networks.
Domain Verification – Google has partnered with GoDaddy and eNom (domain registrars) to make it easier to verify that you own a domain (and can use/access Webmaster tools). Instead of coding, there’s an easy pop-up interface. Just GoDaddy and eNom for now, but more coming.
There’s also a new Browser Size tool. This shows you what parts of your page are showing up “above the fold” (meaning without scrolling), and which links are getting clicked. It’s in the in-page analytics page.