Hoover Stock Photography

http://www.hooverstock.com/

Hoover Stock Photography is an online image library where you can purchase / download beautiful pictures for your web projects. Two kinds of pricing levels are available: Free (requires that you link back to the service) and Pro ($1 to $2 for each image and no link back required). You don’t need to register to download the images but you must create an account if you want to make a purchase.

All pictures are available in high-quality, JPEG and EPS formats, and they vary in size according to the resolution they were shot.

Studio7Designs

http://www.studio7designs.com/stock-photography/

Studio7Designs is a free, nature-oriented photography website which publishes free images under a Creative Commons 3.0 license, that you can use for all purposes. Studio7Designs only asks you to link back to the service as a sign of acknowledgement of their work.

All images available on the site are offered in high-quality, in the JPG format, in different sizes. You can download them just with a simple right-click.

Springer Images

http://www.springerimages.com/

Springer Images is an online image library where you can find over 2.8 million royalty-free stock photos focusing on scientific, technical and medical fields that you can use for noncommercial web purposes. You need to register before downloading any image from Springer Images.

All photos are high-quality and available in the JPG format and different sizes. You can also customize specific sets of images and export them to use on your web projects. If you subscribe to the service, you can also browse Springer Images catalog from your iPhone, iPod Touch or iPad.

Wellcome Collection

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

Wellcome Collection is an online stock photography library where you can find stock images devoted to medical and social history, contemporary healthcare and biomedical science, all released under a Creative Commons license. Registration is not mandatory to download the images, but by signing in you can take advantage of the lightbox feature which allows you to temporarily save online the photos you like while you keep on browsing the archive.

All stock photos are available in high-quality, JPG format and they vary in size. To download them, just right-click the photo you need and then choose "Save As...". Print versions are also available upon request.

Digital Images for Education

http://imagesforeducation.org.uk/

Digital Images for Education is an online project from JISC Collections where you can find a lot of images that focus on the education field. There are over 56,000 royalty free images coming from ten different sources and their usage is limited to academic purposes only.

All images are available in high-resolution, in TIFF and JPEG formats, and they vary in size. You can download each image with a simple right-click procedure and save it to your computer.