Dock is an addon that, as the name suggest, allows you to shrink and dock other frames into it. On mouseover frames can be zoomed in letting you take a good look at their contents.
Virtually infinite amount of docks, or just one if you'd like
Practically any frame can be docked by just dragging and dropping
Highly customizable: colors, animations, orientations and more
Tabbing feature that lets docks be collapsed even further
Load on demand configuration, no reason to waste that memory
You can view a video of Dock here:
You can view a video of Dock's tabbing features here:
The Dock wiki with FAQs is here:
Dock is still considered beta, please treat it as such.