How to tell which SQL Server version, service pack, edition, etc. is running

Execute the following query:

SELECT  
    SERVERPROPERTY('productversion') as 'Product Version', 
    SERVERPROPERTY('productlevel') as 'Patch Level',  
    SERVERPROPERTY('edition') as 'Product Edition',
    SERVERPROPERTY('buildclrversion') as 'CLR Version',
    SERVERPROPERTY('collation') as 'Default Collation',
    SERVERPROPERTY('instancename') as 'Instance',
    SERVERPROPERTY('lcid') as 'LCID',
    SERVERPROPERTY('servername') as 'Server Name'

 
This useful info came from this blog post.