I recently took a BizTalk course and instructor shared many tools during the course that are tools that are typically used by BizTalk developer but do not ship with BizTalk. Here they are, I am sharing them with you!
WINTERDOM – Pipeline unit testing tool
BizTalk Server Pipeline Component Wizard – must use tool for building pipeline component
Deployment Framework for BizTalk (BTDF).
WCF LOB Framework – for building your own adapter
Microsoft BizTalk Server 2010 ESB Toolkit
BizUnit – unit testing
MessageBox viewer – see health of your message box
PAL – Performance Analysis of Logs (PAL) Tool.
BizMock – mocking webservice, unit testing
BizTalk documenter – to generate documentation