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.
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
PhoneGenerator.net - Generate random phone numbers for all countries using the mobile phone generator. These numbers are fake, but they are built using the validations of telephone numbers.
Apple Contacts App - Access and edit your contacts from personal, business, and other accounts with the Contacts app.
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
FullContact Card Reader - Automagically scan biz cards into LinkedIn/Gmail contacts