Gmail Mail Merge - Send personalized emails with attachments
Dynamic Campaigns by Sigstr - Share the most relevant content in every email
Nova Inbox - Personalize emails in seconds, right from your inbox
Tropical.io - Connect your CRM and other sources (Mailchimp, Unbounce, GoToWebinar, Uservoice, and more) and we tell you which leads are hot
PushMarket - Automate personalized emails for ecommerce (YC15)
Mailmeteor - Send hundreds of personalized emails with Gmail.