Thought I’d collect a few resources to help you guys along the way with some great
articles from Sonu(PM for the .NET
Adapter Framework) :
Well worth a read.

Here is additional information on creating custom adapters using BizTalk Adapter
Framework-
Developing Adapters Using the Adapter Framework
http://msdn2.microsoft.com/en-us/library/ms944509.aspx

Developing Custom Adapters

http://msdn2.microsoft.com/en-us/library/aa559841.aspx

Writing Effective BizTalk Server Adapters
http://msdn2.microsoft.com/en-us/library/ms942193.aspx