Well-dressed Europeans have been combining navy and black for ages. (And as luck would have it, what was shown over at The Sartorialist today? A great shot of an Italian girl in... you guessed it, navy and black.)
One of the many style books I read mentioned it several years ago. And I like it. It's a different twist on monochromatic since the colors are so similar.
It also isn't anything you have to "dare to try." It's actually quite safe without being boring. It's unexpected and sophisticated. So next time you're headed for that navy skirt and white shirt, grab the black shirt instead. Or try the black stockings like Michelle did. I also like a navy top and black jeans with some great accessories. Just make sure your navy isn't too dark, or you'll lose the necessary contrast.
This is definitely a color combo you can put together year after year!