Untyped messages inside an Orchestration allow for many different types of messages to be received by the same Orchestration using System.Xml.XmlDocument. This is an update to the untyped messages sample referenced below in the Related Items section. This uses promoted properties to access data inside the untyped Xml messages.
This sample should work for BizTalk 2004 and BizTalk 2006.
Get more information from the original blog post on this topic: http://www.biztalkgurus.com/blogs/biztalk/archive/2004/09/17/Working-with-Untyped-Messages-In-An-Orchestration-_1320_-Part-2.aspx