Animal Photos is is a comprehensive online stock photography resource where you can find free images (released under 3.0 Attribution-ShareAlike Creative Commons License), dedicated to animals that you can use on all kinds of web projects.
All the free images are in high-quality and available in the JPEG image format in different sizes. To download the free pictures, just right-click on the photos you like and choose "Save As..." to save them to your computer.
Jupiter Images is a library and search engine subsidiary of Getty Images where you can find royalty-free stock photos inside a database of 2.5 million images from over 50 photos collections. You can search for free photos by topic, keywords or collection and you can save your favorite images to a lightbox after you register for the service.
All the free images can be purchased in JPG format and five resolution options: web, low, medium, high and very high and they vary in size depending on the resolution you select. Prices range from $49 to $569.99.
Wellcome Collection is a stock photography library that publishes free images devoted to medical and social history, contemporary healthcare and biomedical science under a Creative Commons license. Registration is not mandatory to download your images, but you need to sign in to save your free photos to your lightbox.
All free pictures are available in high-quality and JPG format and vary in size. To download the free pictures, just right-click the photo and save it to your computer. You can also order a print version of your favorite images on demand.
PPOC is an online catalog of free images which publishes royalty free stock photos and prints devoted to American history and facts. PPOC is an initiative from the Prints & Photographs Division inside the U.S. Library of Congress.
All free pictures are available in high-resolution, varying in size and in JPEG and TIFF file formats (you can choose to donwload in either one of the two). PPOC also offers thumbnail photos in GIF, 150x150 pixels. You can search for the photos by time, period and place and save them to your computer with a simple right-click operation.
EduPic is a stock photography website where you can find a wide range of royalty free images and graphics related to education and subjects from school to use for educational purposes only.
All images are available in high-quality, in JPEG format and the free images vary in size. You can browse a comprehensive list of categories or search for the image of your preference using the internal search engine. You can download the free pictures by simply right-clicking the image and saving it to your computer.
BurningWell is an online stock photography resource where you can find free images to download and use on the web for any purpose without restrictions. The images on BurningWell are released under the public domain and both photographers and users from all over the world can make donations of free photos graciously.
All stock photos are in high-quality and available at a resolution of 1600x1200 pixels or even larger (no maximum size limit) in the JPEG format. To download the free pictures, just right-click the photo and save it to your computer.
FreePhotos.se is a website collecting free images released under the public domain. The photo are not taken by professional photographers, but are updated persistently and they are also syndicated via RSS feed.
All the free pictures are available only in one size and their quality varies (though it is generally high). Each free photo comes with all the info regarding the camera used, its resolution, the date the photo was taken, the photographer, the location, and more. Since all the images on the site are released under the public domain, you have no restrictions whatsoever to use them in your projects.
Ookaboo is a collection of free images, indexed by precise terms from the semantic web. Ookaboo has two goals: to improve the state of the art in image search for both humans and machines, and to construct a knowledge base about the world that people live in that can be used to help information systems better understand us.
All the free images are available only in one size and their quality depends on the photographer (though it is generally high). All pictures on Ookaboo are released under the public domain or under a Creative Commons license, meaning that you can use the free pictures for your creative projects.
RoyaltyFreeImages.net is a blog which publishes royalty free stock photos that you can freely download and use with appropriate credit and link back. New photos are added every couple of days.
All free images are in high-quality and available only in one size. All free photos are suitable for both personal and commercial use either online or offline, but please note that distribution or resale is not permitted on any venue.
The Stock Solution
The Stock Solution is an online stock photography resource where you can find tons of free images and free stock images for complementing your creative projects. New photos are added daily.
All stock photos are in high-quality and available in a large (800x900) resolution and, when available, a link to an even higher resolution is provided. On each stock photo you can clearly see what license is associated with the image and whether the free image is suitable for commercial use.