I want to do something like DataLayer.DataSources("").GetDataTable("SELECT * FROM Table") instead of going through a BO.  I just want a direct query on the database instead.  When I try to do this, the GetDataTable requires another parameter...a callback to be passed to it.  What is this parameter and what do I need to use here?

The callback that is passed is the callback that should be executed for Query Notification Services if the data changes on the server... when the business object is using the SqlDataSourceItem class, you can register query notifications with the server, and the callback is the method that should be called when a notification is received back from the server. 

It's only valid for SQL Server 2005 when Query Notification Services is turned on.