V12 Data - V12 Data offers rich data sets with verified addresses and emails for personalized marketing campaigns.
Google Tag Manager - Google Tag Manager helps make tag management simple, easy and reliable by allowing marketers and webmasters to deploy website tags all in one place.
Adobe Audience Manager - Adobe Audience Manager is a data management platform that integrates online and offline data to deliver a unified view of all your audiences
Segment - We make customer data simple.
Google Audience Center - 3 votes and 6 comments so far on Reddit
RudderStack - Open-Source Customer Data Platform