The more you´ll use computers in education, the more you´ll publish texts and other materials online. The biggest problem with this usually is that you don´t have copyright for pictures you want to use. One way to solve the problem is that you or your students take the pictures needed, but that is not always possible. If you need a picture to illustrate ancient Greece it might be hard to find anything to take a picture of that illustrates that.
A better solution is to use pictures that has a CC-license. CC means creative commons and is explained in part 18 of my series ICT in schools.
Below is a number of sites that offer pictures with CC-licence that you can use. Make sure you read if there are additional conditions.
All links are opened in a new tab/window.
Getty Images has released 35 millon pictures that you can use for non-profit use. You embed code on your blogg/homepage by copy and paste the HTML-code from Getty Images. The picture above is an example from Getty Images. Recommended!
Flickr Use www.flickr.com/commons and www.flickr.com/creativecommons Different license for each picture. You can use the pictures for non-profit, but need to link to the photograph.
Photo Pin Searchtool for pictures. Uses Flickr creative commonlicenses.
Pixabay More than 400 000 pictures. Create an account. Many photographs have a high quality. Clip art is also available.
Wikimedia commons Contains pictures and other media. As usual when it´s wiki, shareable, but some pictures are copyright protected, so make sure what goes for each picture.
CC search A search tool for finding photos with CC-license.
Stockphotos for free Over 100 000 photos. Start by creating an account.
rgbstock Over 100 000 pictures. Requires registration.
Internet Archive Book Images A Flicker page with millions of historical pictures.
Free images Almost 400 000 pictures/images. Start by creating an account.
Free Foto Over 132 000 photos. Says what license goes for each photo. You link to site or picture. You need to register your email before you can use the service.
MorgueFile Limited archive. Uses their own license system.
Europeana A project within EU where they try to get resources from museums, institutions and libraries to a bigger audience. Link back if you use resources from this site.
Fotopedia An encyklopedia containing photos. Read more about it here.
Freedigitalphotos.net Give cred to the photograph. If you want to buy the photos you can. Prices differ from photo to photo depending on resolution and size.
Fotoakuten A Swedish tool that is free as long as you state the source. Limited archive.
Fotofinnaren A swedish tool for schools. Limited archive.
Freerange Start by creating an account.
Stockvault Create an account.
Good Luck finding pictures!