WP-UserOnline gives you details about who's viewing your blog
Most statistics packages focus on which pages or content are drawing people to your site. While that's certainly important, sometimes you want to know what's happening right now in terms of traffic on your site.
If you're running a self-hosted WordPress blog, you can install a plugin called WP-UserOnline to find out exactly that. WP-UserOnline gives you a summary of who is currently viewing your blog broken down by Members, Guests, and Bots. It then gives the details for each one below, including the member name, name of the bot, the page the user is on, and the referring page (if available).
It's certainly not as full-featured as a full stats package like Google Analytics, but there's no better way to know what traffic is viewing your WordPress blog at the moment.