SQL Server 2008 R2 package configuration

Hi, We are in the process of upgrading from SQL Server 2005 to SQL Server 2008 R2 and re-writing SSIS 2005 packages in SSIS 2008 R2, while doing so want to do away with XML package configurations and make them dynamic using SQL Server and Environment Variables as these packages get deployed in many different environments. Could you please guide me to implement it?

Thanks in advance..............