The Piwik Marketplace is an open Marketplace for Piwik plugins. It is a place where companies, developers and enthusiasts can freely share with everyone their Piwik plugins. The Marketplace is not controlled by a private entity and plugins don’t have to be pre-approved to be displayed: the Piwik Marketplace is open. Of course there are rules that Plugins developers must follow to publish their plugins in the Marketplace.
In other words: the Piwik Marketplace is the equivalent for Piwik to what Google Play is to Android phones, or what App Store is to Apple iOS devices.
Browse the Piwik Marketplace at: plugins.piwik.org