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.
PushEngage - Personalized Browser Push Notifications.
PushBots - Light SDK for mobile push notifications
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.
Morengage Push Notification Tool - Morengage is web push & app push service.
PushCrew - Push Notifications for Websites