http://blogs.conchango.com/jamiethomson/ Jamie Thomson - Life, the universe and SSIS!

http://www.sqlis.com/

http://microsoftdw.blogspot.com/ Scott Barrett has begun a blog dedicated to implementing Microsoft BI technologies

Marcin Policht
Databasejournal
SQL Server 2005 - SQL Server Integration Services - Part 1 -12

Kirk Haselden blog - Development Manager for SQL Server Integration Services

SQL BI

Business Intelligence with SQL Server (by Marco Russo) 

SQLServerCentral.com

Examples of SSIS Variable Usage
If you want to know how to use variables to control your package flow go here: http://www.sqlis.com/default.aspx?306
If you want to use variables in expressions to set properties of a task (termed property expressions) then there's a nice example here of setting the SQLStatementSource property of an ExecuteSQL Task: http://blogs.conchango.com/jamiethomson/archive/2005/06/11/1593.aspx
or here of setting various properties of the SendMail task: http://www.sqlis.com/default.aspx?59
or here of setting the ConnectionString property of a FlatFile connection manager: http://blogs.conchango.com/jamiethomson/
explains how expressions can also be used in a variable: http://blogs.conchango.com/jamiethomson/archive/2005/03/19/1163.aspx