HP began its OpenStack-based Cloud Services this month, and there is a lot of promise but not much in the way of actual implementation yet. HP intends its cloud to cover both public and hybrid uses. Initially, the beta is free of charge although you will need to provide a credit card number for authentication (you won't be charged anything while the beta is underway).
There are two main services initially available: compute and storage, roughly equivalent to Amazon's Web Services and S3. Compute servers come in four different varieties of Linux initially, although HP plans on adding more and expanding to Windows servers too. Each server can have a public IP address and to get started you need to do an SSH terminal session to install various packages, and set up the cloud storage and attach to this particular server. The Web control panels are somewhat spare, to say the least:
Speaking of command lines, HP's Cloud is very fond of them. Your choices are to use the Linux/Mac OS standard commands, or to run the Windows Powershell commands or Eucalyptus Euca2ools. There is more documentation on the various open software APIs they use here.
Think of what HP is doing as the wild west of cloud computing, compared to a dense urban environment that has been built out by Amazon and others. The idea is that you can grab your own 40 acres and build your environment as you see fit, provided that it is Linux-based and you don't mind digging around the docs and forums to get help. Perhaps you can bring up your cloud solution faster than in AWS, but it would be nice if HP gave you a head start with being able to import AWS AMI's for example.