I just got a cool reference website in my Twitter feed that is worth sharing! The site is called Fotopedia and it is a visual encyclopedia full of images and information!
All you do is search the site based on the subject or topic you are teaching. Some examples I tried were Landforms, Fish, Texas, Presidents, etc. Your results bring you a collection of photographs illustrating the subject along with an informational description with links to Wikipedia articles**.
Check it out!
** As with all things Wikipedia, make sure to take facts with a grain of salt since anyone can add information. This is another great avenue to discuss with students how not everything you read on the web is the most reliable information and to search with caution. :)