Ivan Peev's article about SSIS scripts has been posted on MSDN.
Check it out here: http://msdn.microsoft.com/en-us/library/dd129901.aspx
It contains good introductory information about setting up and creating SSIS scripts. You will also find valuable information how your SSIS scripts can be boosted with CozyRoc's enhanced Script Task Plus. There is one piece of missing information worth mentioning: the article describes the scripting in SQL Server 2005. A similar Script Task Plus is available for SQL Server 2008 as well. Enjoy!