Here are the list of Biztalk trial version you can download and install. Normally 120 days evaluation version. You can also try the Virtual labs, if you don't want to spend time installing BizTalk server and all its dependencies.
BizTalk Server 2006 Exam (70-235) Preparation Diary
BizTalk 2010: Line of Business Systems Integration Kent Weare , Richard Seroter, Sergei Moukhnitski , Thiago Almeida, Carl Darski
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..