Brooklyn Neighborhoods Map
I remember when I was looking into moving to Brooklyn and it was hard to find a decent map of the neighborhoods. Sure, the Dept of City Planning has their City of Neighborhoods map, but that doesn't even have street names on it. You can usually get a decent idea of neighborhood boundaries by looking up a neighborhood on Wikipedia, but that's just a text description.
I thought surely someone must have overlaid neighborhoods on Google Maps. It took a little digging, but finally found this Brooklyn neighborhoods map on Google Maps, created by a user named nfolkert. Exactly what I was looking for (and was afraid I was going to have to create). Clicking on a color-coded neighborhood polygon will pop up the name of the neighborhood and its boundaries as described on Wikipedia (if available), as well as a link to the Wikipedia entry.
Of course, the exact boundaries of a neighborhood are often debatable. What residents will tell you and what realtors will tell you are usually two different things. But, this map is a great starting point for anyone wanting to get an idea of where the neighborhoods are in relation to each other (or if you want to verify the validity of a sales/rental listing).