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.
PushCrew - Push Notifications for Websites
Wise Notifications - The only solution to send notifications to your iOS website visitors, without creating an iOS app yourself. Increase your revenue by retaining your valuable website's iOS visitors. All other web push notifications are missing this. Setup in 5 min.
Amazon Pinpoint - Targeted Push Notifications for Mobile Apps
PushOwl - Re-engage website visitors with push notifications
PushEngage - Personalized Browser Push Notifications.