Trystack is a sandbox installation of OpenStack sponsored by Dell, NetApp, Cisco and Red Hat.
You'll get a free access to test your stuff on Trystack, but there's one important rule:
Rule No. 1: Remember that TryStack is designed exclusively as a testing sandbox. We wanted a fast, easy way for developers to test code against a real OpenStack environment, without having to stand up hardware themselves. It probably goes without saying that this is not the place for production code - you should host only test code and test servers here. In fact, your account on TryStack will be periodically wiped to help make sure no one account tries to rule tyrannically over our democracy. Play nice in the sandbox!
In order to get access you need to use your Facebook account to log in.
IMPORTANT NOTE: In order to log in with the Facebook link, you must be a member of the TryStack Facebook group. API access is available by resetting your password in the web interface using the settings for your account and selecting API Access.
Once you've joined the Facebook group and logged in, you'll find yourself quickly at the rather empty OpenStack view.
If this is your first time testing OpenStack, you'll probably want to click Images, choose one and click Launch Instance.
You won't be able to login into your instance as root password, you'll need to upload your SSH public key first. This seems to be the most common question on the user forum...
Now you are own your way becoming the next OpenStack expert. Have fun!
And once you are ready to setup your own OpenStack installation, go to https://www.rdoproject.org/ for free community version of OpenStack or to http://www.redhat.com/en/technologies/linux-platforms/openstack-platform for Red Hat's enterprise version.