OpenStack is a complete free and open source cloud operating system and management platform that has a large backing in both the open source community and enterprise server and data center industry. There are many uses for OpenStack, including both public and private clouds, but if you ever want to test an application or development tool on it, you will need the infrastructure to deploy it. Fortunately, a service called TryStack offers free OpenStack testing on its servers.
TryStack has clusters running on both x86 and ARM architectures. You are free to try an instance of OpenStack over a 24-hour period, after which the space will be reclaimed for others to use. TryStack offers three base server images: Ubuntu 12.10, Fedora 17, and Fedora 18.
Once you have your server instance up and running, you will have access to the dashboard and can go to town testing your applications or setup configurations that you might plan to run when you actually deploy OpenStack on your own servers.
TryStack is only for testing. Your data will be deleted after 24 hours, so there would be no point in using it as a production server. During that time period, however, you can learn a lot about the code you are developing and testing. Furthermore, once your first instance has been deleted, you can create more in the future to continue testing.
TryStack is just one option for testing OpenStack. You could always install it on your own spare server, if you have one available. You could also install it on a standalone machine. The advantage of TryStack is that you do not have to worry about setting up your own hardware, and the test images are already configured and ready to go.