Visuwords is a cool online graphical dictionary that helps the user "visualize" the meaning of a word in many of it's forms. For students, it's a great alternative to old school dictionaries. Enter a word and Visuwords will produce diagrams (that look a little like a neural net) so the user can learn how words associate literally at-a-glance.
You can click and drag to pan around and zoom. Hover the cursor over nodes to see the definition and click and drag individual nodes to move them around to help clarify connections.
You don't need to sign up for an account or sign in. Just book mark this page or even write the link on the board - www.visuwords.com and it's a quick click for students to have an alternative for vocabulary study.