Lots of high quality photos in a variety of categories. Please note: this website is about to move to another hosting provider, so you may have to Google "Open Photo" if this link is broken.
This website was created by an educator, for educators. Mr. Vann clearly states that his photographs and drawings are free for use without permission. Images are organized according to subject area.
Wylio is a search engine that browses images with Creative Commons licensing. This website was originally created for bloggers to find pictures. The free version allows you to search, resize, and embed the code (with credits) into your presentation. The subscription version ($2.99/mo) allows you to specify pixel size, download, and remove ads.
Large photo gallery with 7000-1000 new photos uploaded monthly. Photos on Photl are exclusive to Photl, so you won't find any repeats from other stock image sites. You are permitted to download up to 40Mb per day. There is a small fee if you are using any pictures for commercial use.