Pusher Beams - Send push notifications programmatically at scale
PushCrew - Push Notifications for Websites
Pingy - Check your site status from your menubar
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.
Snowball Smart Notifications - Get the notifications you want and none of the rest
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.