As we know SQL 2008 R2 is already released, it is a good time to start using SQL 2008 R2 for testing and implementing in your environment. Microsoft already released the free expression versions for all.
Please click below links to download a free copy of SQL 2008 R2:
Microsoft SQL Server 2008 R2 RTM - Express with Management Tools – Download it from http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=967225eb-207b-4950-91df-eeb5f35a80ee. This is data management system (R2 Express Engine) which comes with Management Studio Express.
Microsoft SQL Server 2008 R2 RTM - Management Studio Express – Download it from http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=56ad557c-03e6-4369-9c1d-e81b33d8026b. This is an integrated environment for accessing, configuring, managing, administering, and developing all components of SQL Server Express.