Tools: SlowCheetah - XML Transforms

If you have different Debug/Release configurations and want to switch them automatically when you run application - this tool is "must to have" for you.

SlowCheetah - XML Transforms
"This package enables you to transform your app.config or any other XML file based on the build configuration. It also adds additional tooling to help you create XML transforms.. Written by: Sayed Ibrahim Hashimi, Chuck England and Bill Hiebert"

Just used it with my application, it works like a charm, no more lines of code in build script changing configuration for production environment. 
Highly recommended!