Here is the collection I noticed. If you have some more, why not sharing them!
Mathematics : Mandelbrot Fractal Browser
With this project, you can navigate through a mandelbrot fractal frame.
You can zoom in or out. All along your navigation, you won't get lost in this infinity of forms thanks to the overview map.
OpenLayers was obviously the most convenient technology for this kind of displaying.
This website makes intelligent use of the resolution configuring, the zooming capabilities and ergonomic characteristics of OpenLayers.
Biology : Genome browser
What if, in the same manner as above, you could explore the genome?
That's what this website allows you to accomplish.
The coordinates are, here, replaced by the base pairs position and each genome's area is georeferenced.
A click on a region triggers the display of its characteristics.
The code is avalaible on google code. If you're curious about it, check it out here.
Gaming : Pentamino puzzle
This website demonstrates extensive use of OpenLayers' Vector Capabilities.
The build of such an interface is a real technical challenge.
Communication : Rosetta Project
The rosetta project aims at building an archive of all the languages in the world.
A very rich image representing the Earth with languages labels emerging from the continents helps you find your way in this tremendous collection.
With such an attractive and interactive homepage, you want to go deeper into the subject.
These examples show localization in fields where it wasn't expected.
It shows some very clever uses of OpenLayers. For some of these applications, one might have first thought of other technologies like Flash, but as we can see, the light-weight OpenLayers library really does the business good.