A friend of mine recently started a blog called Dirt and the City and, because he has invited me to contribute to it, I feel like posting a reference here ;-)
Dirt and the City is a blog that intends to show you the "ugly" (literally) side of NYC. The blog is named after a famous TV show filmed in this same city; I haven't watched the show myself, but I bet that there is no dirt to be seen in it. If you are wondering what the city really looks like, this blog is your place.
But, before visiting the blog, be sure to take it as it is meant to be: just a fun collection of photos! If you ever want to visit NYC, don't let the contents of the blog change your plans. You will definitely enjoy your visit regardless.