While I was searching for images for a project, I came across Photos Public Domain, which offers images of various quality with a decent range of subject matter. The site doesn’t have thousands upon thousands of images, but there are quite a few gems. The best part is they are, as the name implies, public domain, and free for commercial use. Donations are accepted of course, but not necessary. I particularly liked the holiday collection.
Grab this free Photoshop Action file to create a realistic simulation of a letterpress business card. Handy for presenting mockups to clients.