DigitalOcean - Simplifying cloud hosting. Deploy an SSD cloud server in 55 seconds.
Socket.io - Realtime application framework (Node.JS server)
CloudVPS - VPS Hosting in a reliable, scalable and fast cloud | CloudVPS
Ably - Serious realtime infrastructure
Microsoft Azure - Windows Azure and SQL Azure enable you to build, host and scale applications in Microsoft datacenters.
Pusher - Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.