EmailDrips - Get inspired by examples of email sequences
SendLater - Email scheduler for Mac Mail.
Clearbit Salesforce - Rapportive for Salesforce, augment lead data
SndLatr - SndLatr is a Gmail plugin that makes it easy to schedule emails to be sent automatically at a later time.
Lite Pae - A fully native Salesforce app to capture payment using Stripe
RGB Technologies - Email Scheduler - Email Scheduler provides an intuitive email scheduling solution, integrated within the existing Salesforce account.