Compare Database Schemas
One of the great things about PowerShell is the strength of the PowerShell community. This is shown by the number of people sharing their PowerShell scripts.
A good example is the script to compare the schemas of two SQL Server databases that Steven has written - http://blog.usepowershell.com/2009/02/comparing-database-schemas/. This could be valuable if you work in an environment where databases are frequently changing. This can also be used to give an audit trail of change over time.
It is also a good example of how to interact with SQL Server from within PowerShell.