New York Public Library Pictures for free

The New York library has released 180,000 images for free that you can download.
The resolution is massive so images can be printed out at poster sizes no problem.

Check out website and links at:

http://digitalcollections.nypl.org/

http://www.nypl.org/research/collections/digital-collections/public-domain

Here is a sample from the 'Changing face of NY' collection with some Lightroom versions.

original

lightroom version 2

lightroom version1

lightroom HDR version