Google Analytics - Improve your website to increase conversions, improve the user experience, and make more money using Google Analytics. Measure, understand and quantify engagement on your site with customized and in-depth reports.
V12 Data - V12 Data offers rich data sets with verified addresses and emails for personalized marketing campaigns.
Histats - Start tracking your visitors in 1 minute!
Lotame - Make your data actionable, learn about your most valuable customers, improve ROI by targeting the right audience and increase relevance across screens.
StatCounter - StatCounter is a simple but powerful real-time web analytics service that helps you track, analyse and understand your visitors so you can make good decisions to become more successful online.
Google Audience Center - 3 votes and 6 comments so far on Reddit