1. Wikimedia Commons and Mayflower
Wikimedia Commons has a database of 1,780,830 freely reusable media files, including audio, video, photos, illustrations. It provides you with a handy search tool Mayflower to find the right image with the information about its permissions.
Stock.XCHNG definitely lives us to the site owner's claim to be "the leading FREE stock photo site". With its database of 326050 photos that updated with hundred of new images on a daily basis everyone will always be able to find the needed pictures for their projects. It requires a free registration and be sure to read the permissions details before downloading the file, some may require you to give credits to the photographer.
MorgueLife contains free high resolution digital stock photography for either corporate or public use. It quickly became my new favourite site when looking for stock photos online. Many of the photos there are offered in really high quality with the sizes reaching up to 3072 x 2304.
Stockvault allows you to share and download over 8.000 royalty free, high resolution stock photos, templates and logos. It also offers helpful tutorials on anything from 3D Studio Max to Photoshop to CSS to PHP.
Wallpaperstock - is an excellent resource for Free desktop wallpapers and stock photos. Image sizes range from 1024×768 to 1600×1200.
Photogen stock photos are FREE for commercial and personal use. "Forget royalty-free - try totally-FREE."
Everystockphoto - Searching Over 1 Million Free Photos, results include pictures from Flickr, stock.xchng, Imageafter and many other image resources. Be sure to check the license for using Flickr images.
Yotophoto is indexing over a quarter million Creative Commons, Public Domain, GNU FDL, and various other 'copyleft' images. I really like how it's returning the results by displaying three important details underneath each of the found pictures: source site, license and image size.
So here you go, hopefully those 8 bits above will help you to save some money.