OSDragonDemos
Open Sea Dragon Demos
One Direction - View A tweaks impact view B, but view B tweaks don't impact view A. Good for working with misaligned images.
Magnifier - Create a coordinated magnified window following the cursor in the original window.
Preferences - Keep (somewhat) persistent viewer preferences.
State Links - X, Y, and Zoom are encoded in the url for easy sharing.
(WIP) Polygon Draw - Draw and manipulate a polygon, then set it to work with the view.