Well this is a pleasent surprise. I started tinkering with Sean O'neils sample code about atmospheric scattering [Edit 01/2008 - but his site has since gone away). His implementation was in GLSL and I'm working with DirectX (.NET FTW). I actually managed to copy and paste the shader and fix it up and it mostly works. It's amazing what some nice shaders can do to make things look nicer. I think this is pretty good for my first HLSL program ;)