Architectuul is an online architecture catalog that uses crowdsourcing to build content. It was founded in 2010 by a team of architects, graphic designers and software engineers. All of the content and images uploaded to the site use the creative commons license, making the process similar to Wikipedia. Architectuul has buildings from various era's with a large range from the 20th Century and rare Constructivist architecture.
Architectuul is utilised as a source by several publications and Universities, including the Wall Street Journal.
References
Architectuul Wikipedia(Text) CC BY-SA