Seth Godin shares this morning that Flickr can be a great source of photos for a presentation or website or brochure.
Go to advanced search, choose Creative Commons Commercial license and search away. The breadth is extraordinary, but what will amaze you is the quality. And the license is a generous gift from the photographer to you.
You may need to give attribution the photographer (perhaps linking the photo back to flickr account) and be limited in altering the photo. Check details on the various Creative Commons licenses at Flickr.
Seth says to be sure to check out the HDR images, and don’t forget to sort by “Most Interesting.”