I've been working on a C# port of the Flixel game engine. (a popular Flash AS3 game engine) The port I'm working on uses OpenTK for rendering, sound, and input. I've been trying to integrate GTK# into it to allow for some windowing GUI features. Specifically, you can't hide the mouse properly with just straight OpenTK. GTK# allows for this feature. I'm trying to make sure that this port is fully cross-platform compatible. I'm developing it with cross-platform tools, and testing it regularly on my PC, Linux, and Mac machines. 
 
My current progress is encouraging. I've gotten the FlxSprite class working, as well as most of the basic classes. I'm currently working on re-tooling the FlxGame class as a GTK# widget, so that I can use the mouse-hiding feature of GTK#. As soon as I'm finished with that I will be able to return to developing some of the more game-centric features of the engine. 
 
I'm also considering starting work on a Giant Bomb guide for one of my favorite games, King's Quest VI. I like to replay this title every other year or so, and I'm about due for another run-through. I wouldn't mind writing up a comprehensive guide while I'm at it.