Following links are best starting point for ESB Toolkit.
http://abhijitmahato.wordpress.com/2010/09/10/biztalk-esb-toolkit-2-0-samples-content-based-routing/
http://www.codeproject.com/Articles/293385/Dynamic-message-processing-and-routing-in-Itinerar
http://www.codeproject.com/Articles/288285/Hello-World-in-BizTalk-ESB-Itinerary-using-a-Purch