Plone 3.1 is available on Objectis
Plone 3.1 instances are available on Objectis site, live a new experience with this version who has many new features.
So ask for your Plone 3 instance on http://myplone.objectis.org, explaining motivations for your request. The staff will then validate your request and you'll reveive a validation code. With that code you'll be able to create your instance with the form on http://www.objectis.org.