Certifications allow you to prove your competitive skills across the breath of the product. Some people say "It's too theoratical, they never test your real world experience", but I feel you need to know the breath of the product to pass the exam which will help you to learn what's there in the first place.
BizTalk Server 2006 Exam (70-235) Preparation Diary
Pro Mapping in BizTalk Server 2009 Jim Dawson and John Wainwright
Professional BizTalk Server 2006 Darren Jefford, Kevin T. Smith, Ewan Fairweather
SOA Patterns with BizTalk Server 2009 Richard Seroter
BizTalk Server Operations Guide Provides recommendations and best practices for configuring, testing, maintaining, monitoring, and optimizing.
Performance Optimization Guide Consolidates and provide guidance on the best practices and techniques to optimize BizTalk Server performance.
Business Activity Monitoring in Depth for Developers This paper provides a deep, low-level review of how BAM works and how BAM can be extended.
BizTalk Server 2009 Hyper-V Guide The purpose of this guide is to provide guidance for using Microsoft BizTalk Server 2009 with Microsoft Windows Server 2008 Hyper-V.
BizTalk Server Database Optimization This paper details techniques for optimizing the infrastructure of a BizTalk Server system..