Google images has a lot of cool graphics http://images.google.com/
Google Photo at https://photos.google.com/ allows instructors to create albums by course or subject that students can contribute to and share
Flickr at http://www.flickr.com
Library of Congress Digital Collections at http://www.loc.gov/pictures/ This is a site that has an extensive digital collection. You only have to pay for images that you actually want to reproduce.
Dreamstime at http://www.dreamstime.com/free-photos has a collection of free and inexpensive images.
Istockphoto at http://www.istockphoto.com/ Another great site. There is an option for users to purchase one photo at a time instead of using the credit system.
Free PowerPoint Templates can be found at the Rapid E-Learning blog http://www.articulate.com/rapid-elearning/heres-a-bucketful-of-free-office-themed-e-learning-templates-media-assets/
ThinkStock.com A great collection of photos is available at http://www.thinkstock/com/ . Pricing varies depending on the number of images you wish to download in any particular period of time. Images can also be downloaded for free with watermarks on them -- which can come in handy if you are not planning to reproduce the image or use it for commercial purposes (e.g. for coursework in many classes).
Morgue File at http://www.morguefile.com. There are free photos for use in your projects; some request that you give the photographer credit, or to let them know how you used their shots. Others don't even ask for that much. Cautions: The search function isn't great, and the selection can be limited in some areas. But there is a surprising amount of great free content. It's worth seeing if they have what you need.
Paul Alders 17 Daily Life Images (free) - https://community.articulate.com/download/17-daily-life-images
43 Gorgeous Free Nature Images - https://community.articulate.com/download/43-gorgeous-free-nature-images from Unsplash
35 Free City Scene Background Images from Unsplash - https://community.articulate.com/download/35-free-city-scene-background-images
Cacoo at https://cacoo.com/ allows users to collaboratively create and share diagrams. It is free to use
Avatarist http://www.avatarist.com/ This is a free resource which allows users to select (from a pretty big collection) and/or create an avatar
Wordle at http://www.wordle.net/ This a great tool to create "word clouds" from text you provide emphasizing the most used words by size.