push4site.com - Push4site.com service instant browser push notifications.
PushEngage - Personalized Browser Push Notifications.
Gotify - a simple self-hosted server for sending and receiving messages
Truepush - Unleash limitless possibilities with Truepush and save up to $600 monthly. Free up to 10K Subscribers on all features.
Amazon SNS - Fully managed pub/sub messaging for microservices, distributed systems, and serverless applications
Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop