From AnyGeo, via Donna:

There's an easy way to search for all KML files available on the web: using Google Search, simply enter the following string to search for a KML file for Brooklyn:

filetype:kml brooklyn

or

filetype:kmz milwaukee

Note the vast number of results… you can refine your search or add even more detail if you'd like better results. Similarly, if you'd like to locate an AutoCAD DWF format file, try this search string:

filetype:dwf brooklyn