Identification of SQL Server Edition and Version

This query can be used to identify the SQL Server Version and Edition currently in use on a server.

SQL 2005
SELECT SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY ('edition')

SQL 2000
SELECT SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY ('edition')

SQL 7.0 and earlier
SELECT @@VERSION

The following is a KB article for this.
KB 321185: How to identify your SQL Server version and edition