OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
Mailshake - Mailshake lets you build your professional network through a smart and intuitive approach to cold emailing.
PushBots - Light SDK for mobile push notifications
Cold Email Hacks - Proven cold email templates and tactics for B2B startups
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.
PushCrew - Push Notifications for Websites