My collegue and I were searching for a handy solution to login with a different account then the login-account for the server. We find the following solution:

But this can be automated using the command-line options. If you like to see the list of available command-line options, go to Start > Run > type “SSMS /?”:
This will display the all available options which can be used with SSMS,

The options are self-explanatory, the -E is used for Windows Authentication. – U, – S are used for SQL Server Authentication Both should be mutually exclusive. if you used together the SQL Server Authentication will take precedence. for example, to connect to default instance of local SQL Server execute below from Start > Run or from CMD.
SSMS –S(local) –E
– connect to default instance using Windows Authentication
SSMS –S(local)\InstanceName –E
– connect to named instance using Windows Authentication
SSMS –S(local) –U sa –P P@$$w0rD
– connect to default instance using SQL Server Authentication
SSMS –S(local) –E –U sa –P P@$$w0rD
– connect to default instance using SQL Server Authentication
– SQL Server Authentication takes precedence
SSMS –S(local) –E C:\MyQuery.sql
– connect to default instance using Windows Authentication
– and open a saved query file
SSMS –S(local) –d AdventureWorks2008R2 –E
– connect to default instance using Windows Authentication
– and change context to AdventureWorks2008R2 database
All the options described above are for SQL Server 2008. The same options can be used with SQL Server 2005. However, for SQL Server 2005, replace SSMS.exe with SqlWb.exe.
This article was written down by Vishal