Parse is a backend as a service provider -- originally for mobile apps, but eventually for all kinds of applications. You could store data, manage users, target and send push notifications, gather analytics, etc., all without having to build your own backend.
Nice, that sounds useful. I guess it's good that they're releasing some of it as open source then. :)
I've built a couple backend systems for mobile and other, I've used Kafka/zk for messaging primarily.
I'll have to check this out more in depth, thanks :)