Nova Inbox - Personalize emails in seconds, right from your inbox
Product School - The global leader in product management training
SendX.io - SendX (https://sendx.io) provides remarketing and retargeting tools for web businesses. You can use popups, landing pages, email, web push notification, automation workflows and FB / Google retargeting to drive more revenue.
The Product Manifesto - Product Managers face the biggest challenges of our day, which is why our community needs a common set of product principles.
Mailblast - Email marketing on a budget using Amazon SES
Intercom on Product Management - The ultimate resource for aspiring product managers