Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
BuiltWith - Find out the technology behind websites
Open Contacts - Open Contacts is an advanced address book program for managing contact info of individuals and...
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
FullContact Card Reader - Automagically scan biz cards into LinkedIn/Gmail contacts
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.