Openshift is the PAAS cloud provided by Redhat and can serve as a good development ground and also host drupal projects in production.

Since January 2013, the service allows Drupal 7 installation.

1. Create an account on OpenShift.
2. Once you have signed in create an application. You are allowed a maximum of three applications for testing. Choose Drupal from the array of applications presented to you. Alternatively you could install a PHP 5 application and then build drupal on that. It's a bit tedious though.
3. Provide details for the application i.e. the name. The rest of the customisations can be carried out after the installation is complete. Let the install run to completion. It's pretty quick. When the install finishes you have Drupal 7.7 in your hands.