http://newrelic.com/
A system to monitor multiple aspects of a live application in production including the page load times, server load times, mysql response times, javascript render times, and so on. Expensive.
http://www.woopra.com/
Woopra is a free web analytics tool with a focus on real time analytics. Track visitors live, even talk to them in real time.
http://crazyegg.com/
Crazy Egg adds a new dimension to analytics. It includes a heatmap where you can see where users are clicking on the screen, and other visual presentation tools. From $10 for 10 pages (10k pageviews), up to $100 for 100 pages (100k pageviews).
http://haveamint.com/
Mint is a self hosted web stats package, commercial, about $30 per domain (I think) as at May 2008.
http://piwik.org/
Piwik is an open source alternative to Google Analytics. It uses the same type of javascript tracking, but is self hosted. It also has an extensive plugin architecture, so you can add / remove features fairly easily.
http://getclicky.com/
Web Analytics system similar to Google Analytics that supports live "spy" view that shows page views as they happen.
http://wordpress.org/extend/plugins/stats/
Use WordPress.com's stat service on your standalone WordPress blog.
http://www.openwebanalytics.com/
An open source web analytics framework with in-built integration for WordPress and MediaWiki.
