Night photography is A LOT of fun and can offer a new vantage point in which to shoot. One area I have been working on is using street light, riot light subjects in black and white. Some of the areas you get into can be pretty seedy, but bring a friend with a bazooka to stand guard, and you should not have any problems.
Street light gives a very sharp, one directional light that accentuates texture and sharpens the lines of the subject before the lens. I personally try not to include any light sources into the image, but focus on what is illuminated by the light source.
Street light also mutes the contrast, but don't try to increase the contrast with n+1 development or filters. Just shoot what is their. The effect has a feel all its own. If you are an insomniac, give it a try.