As a " fan", I am a heavy user of developer orgs. Developer orgs are environments, which allow you to test out any of the propositions offers. Communities, Sales Cloud, Service cloud, you name it; everything is there. Signing up is easy and free. You can do so here. Sometimes developer orgs serve as playgrounds for new technology, at other times I actually try to build apps or construct proofs of concept. In most cases these developer orgs are more than enough to achieve whatever purpose I had in mind.