Popsters - Analyze your social media pages and spy on your competitors
BuiltWith - Find out the technology behind websites
CleverAnalytics - Competitor analysis & tracking of customer loyalty software
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
Kompyte - Track & analyze competitors in real time.
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.