Animal Photos

http://animalphotos.info/a/

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

http://www.jupiterimages.com/

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

http://medphoto.wellcome.ac.uk/

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

http://www.loc.gov/pictures/

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

http://www.edupic.net/index.html

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.