The major processing here was in NIK Silver Efex Pro-2. One of the things that I like about SEP is "selective colorization", which allows you to bring back some of the underlying tones in a processed image. It is never really the same as it was originally because you are restoring the color after the B&W process has been applied, but I find that the results are often interesting.
This was shot RAW in the middle of the day with a clear blue sky and bright sun. In SEP-2 it had the "high-contrast; harsh" process applied, followed by a red-filter to darken the blue sky even more. The yellow and lower reaches of the sky then had SC applied with a series of control-points. Although I am not usually fond of cutesy frames, I also added a thin white border in SEP-2 to help separate the now black sky from the back background (which is where this should be viewed).
I have another version of this where I also did a "replace color" in PS-CS5 to turn the bottom of the sky a reddish color simulating twilight. That effect was a little too convincing however, and I think that I prefer this version because the stark bi-color is a bit surreal and menacing.
View On Black
Fujifilm X-100; ISO-200; f8; 1/750-sec; 0ev