As mentioned in a number of posts, there is a clear trend away from Platform-specific PaaS (where you write your application to the platform) and Language-Specific PaaS (which provide support to one or possibly a couple of languages) to Universal PaaS, which is capable of supporting any language and any platform. There’s a little bit of a gray area, but we would include ActiveState Stackato, AppFog, dotCloud, GigaSpaces Cloudify, Red Hat OpenShift, Salesforce Heroku, Uhuru Software AppCloud and VMWare CloudFoundry in this category. These vendors differentiate themselves by providing a broad range of Application Services or Application Lifecycle Services.