Real-time data is a big deal and here are a few popular services I've used to build web apps.

I went ahead and organized this a bit differently. I tried to organize the various services available for distributing data and their relationship with you.

You own, manage and distribute your own data

Do It Yourself

You own your data but let someone else to manage and distribute it

Infrastructure as a Service

Let someone else own, manage and distribute your data

Web 2.0's monopoly platforms

Let someone else own your data but you manage and distribute it