If you want to use Oracle cloud computing for oracle.You must register in oracle website to use for trail period because it is not free.You can register for user account.You can use this url to register:=>
Oracle Cloud is a broad set of industry-standards based, integrated services that provide customers with subscription-based access to Oracle Platform Services, Application Services, and Social Services, all completely managed, hosted and supported by Oracle. With predictable subscription pricing, Oracle Cloud delivers instant value and productivity for business users, developers and administrators.
Oracle Cloud is available to anyone who finds it useful and its features suite their requirement. You can use Oracle Cloud for educational purpose as well. You can use the trial service available as well as you can purchase the service as per the options available.
For Pricing information you can check this link.
In addition to resources posted on Oracle.com and the Oracle Technical Network, Oracle Partners can find additional information on the Oracle PartnerNetwork at www.oracle.com/partners/goto/cloud In the OPN Cloud KnowledgeZone, Partners can find posted an FAQ on the Cloud Programs and Specializations that are available.
Oracle University Provides cloud courses. Please check the link below,
There are also other Clouds like AMAZON,RACKSPACE,etc.
They are different to manage, but once you log into the instance its all the same as a physical box.