WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
FullContact Card Reader - Automagically scan biz cards into LinkedIn/Gmail contacts
MySignature - MySignature is FREE Email Signature Generator that helps to create Professional Signatures for major email clients such as Outlook, Gmail...
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.
Sigstr - Email signature marketing
Nextcloud Contacts - The Nextcloud contacts app is a user interface for Nextcloud's CardDAV server.