I finally took the effort to buy a new camera. It's a Nikon D70. I decided against buying one of the (crappy) bundled lenses but instead bough a f=1.2 55mm second hand. As soon as I got the camera and lens assembled I started playing with it ofcourse, and fortunately the sky was looking really nice.
I'm not sure how this effect occurs, but the sun is already below the horizon and shining from below on the clouds. If anybody can explain why it colours so nices, please leave a comment. You can find a high(er) resolution version here .