There is an extremely good book on BizTalk mapping that has been recently released. Great value to any developer. Includes excellent EDI samples.
Pro Mapping in BizTalk Server 2009
http://www.amazon.com/Mapping-BizTalk-Server-Experts-Voice/dp/1430218576/ref=sr_1_4?ie=UTF8&s=books&qid=1239909911&sr=8-4
