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Wiktionary
Wiktionary ( , ; rhyming with "dictionary") is a multilingual, web-based project to create a free content dictionary of terms (including words, phrases, proverbs, linguistic reconstructions, etc.) in a large number of natural languages and a number of artificial languages. These entries may contain definitions, images for illustration, pronunciations, etymologies, inflections, usage examples, quotations, related terms, and translations of terms into other languages, among other features. It is collaboratively edited by volunteers via a wiki. Its name is a portmanteau of the words wiki and dict
Wiki Loves Monuments
annual international photography contest, organised by Wikipedia community members
Anki
Anki (, ; ) is a free and open-source flashcard program. It uses techniques from cognitive science such as active recall testing and spaced repetition to aid the user in memorization. The name comes from the Japanese word for "memorization" ().

GLtron
GLtron is a 3D snake game based on the light cycle portion of the film Tron. The game is free and open-source software and has been ported to many mobile and non-mobile operating systems such as Windows, MacOS, Symbian and Android over the years.