The default port of SQL server instance will be normally 1433, for more information please refer the below link
http://support.microsoft.com/kb/287932
But It is not necessary that the SQL server instance will operate in the default port in all client places .You can find the port of SQL server 2008 instance by going to .Start->programs->Microsoft SQL Server 2008 R2->Configuration Tools->SQL Server Configuration Manager.
In SQL Server Configuration Manager go to, SQL Server Network Configuration->protocols for MSQLSERVER->double click TC/IP.
Please see the screen shot below for more details
http://support.microsoft.com/kb/287932
But It is not necessary that the SQL server instance will operate in the default port in all client places .You can find the port of SQL server 2008 instance by going to .Start->programs->Microsoft SQL Server 2008 R2->Configuration Tools->SQL Server Configuration Manager.
In SQL Server Configuration Manager go to, SQL Server Network Configuration->protocols for MSQLSERVER->double click TC/IP.
Please refer the below link for more options
http://decipherinfosys.wordpress.com/2008/01/02/finding-the-port-number-for-a-particular-sql-server-instance/Please see the screen shot below for more details
