List of free push-notification stuff for developerππ½
If you're looking for all programming tools around push-notification (not just free). Check this page List of push-notification Programming Tools

Push by Techulus
Receive custom push notifications without building your own app!
Tag: push-notification
Send 100 notifications/month Connect up to 5 devices Email support
Knock
Knock is flexible, reliable notifications infrastructure that's built to scale with you.
Tag: real-time, push-notification
10,000 Free notifications per month Unlimited team members Unlimited notification workflows Preferences support Batch and delay functions

Pusher Beams
A push notifications API for developers who need critical information delivered every time. Scalable delivery for all your apps with no complex integration.
Tag: real-time, push-notification
Sandbox Account 1,000 subscribers