MailChimp's Analytics360 plugin allows you to pull Google Analytics and MailChimp data directly into your dashboard, so you can access robust analytics tools without leaving WordPress.
Site Traffic: Visualize your site's traffic trends and see how blog posts and email campaigns affect overall traffic. You can also isolate traffic coming directly to your site from email campaigns with the "campaign traffic" tab.
List Growth: Chart the growth of your mailing list over time. Compare new and existing subscribers. And if you've got multiple lists, see how they stack up to each other.
Top Referrers: Curious how all that new traffic ended up on your site? Wondering if more people are finding you through search or direct referrals? We'll break it all down for you with Google Analytics.
MailChimp offers other services for WordPress users, too. A list subscribe plugin allows you to easily add a signup form for your MailChimp list as a widget on your blog, and RSS-to-email sends automatic email campaigns to your readers whenever you publish a new post.