Tutorials
Technical and otherwise.
tomic's simple playlist management, and preliminary edits to how to match beats.
This is the Mixxx Wiki - 
Mixxx is a free and open-source DJ software.
Manual
Hardware Compatibility
Reporting Bugs
Getting Involved
Contribution Guidelines
Coding Guidelines
Using Git
Developer Guide
Creating Skins
Contributing Mappings
Mixxx Controls
MIDI Scripting
Components JS
HID Scripting