such that no queen attacks any other queen. It's a simple (really simple) program to write, but I can't remember having done it. So I did it. And then I had to make a picture of one of the solutions.
Addendum: Wikipedia has a page on the puzzle, naturally. This kind of program would be a good one to test out Knuth's "Dancing Links" idea. I might have to do that.
Addendum2: I swiped the chess font and methodology from this website, keeping with my long tradition of drawing stuff on my website using PostScript.
Addendum3: I made a different picture using the Adobe Cheq font: