MacStadium - MacStadium offer Mac colocation and dedicated server rentals plus VMware Mac Pro private cloud environments for large-scale iOS app
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
IBM Bluemix - IBM Bluemix is an open-standard, cloud-based platform that enables users to build, manage, and run apps on mobile, web, and smart devices.
Heroku - Agile deployment platform for Ruby, Node.js, Clojure, Java, Python, and Scala. Setup takes only minutes and deploys are instant through git. Leave tedious server maintenance to Heroku and focus on your code.
Amazon EC2 - Amazon Web Services offers reliable, scalable, and inexpensive cloud computing services. Free to join, pay only for what you use.
Salesforce Platform - Salesforce Platform is a comprehensive PaaS solution that paves the way for the developers to test, build, and mitigate the issues in the cloud application before the final deployment.