The noun project has as its aim the creation of a global visual language through symbols and icons. This could be used for all kinds of vocabulary activities in Communication Arts, Foreign languages, ESOL, etc. Not only can teachers and students use the icons for things like flashcards or presentations, they can create new one and upload.
"Vocabulary.com is comprised of three sections - The Challenge, Dictionary, and Vocabulary Lists. After creating an account, students can immediately begin playing the Challenge's interactive game to build knowledge and create a learning environment on their level. The Dictionary offers basic and advanced searches going beyond just definitions. Explanations and usage examples taken from current publications and classic literature provide a fuller context that helps fortify students' understanding. Thousands of word lists are available in the Vocabulary Lists section which also lets teachers and students create their own word lists based on assignments and personal interests."