The XWiki Store is a collection of paying extensions that benefit from professional support. XWiki is an extensible open source platform for developing collaborative applications on top of the wiki paradigm.
I've designed and prototyped the store design focusing on an extensible repository model. The main objective was to create a design easily scalable and customisable, while allowing each extension to have an individual marketing strategy.
I prefer to interact and create the design in the environment it will live in, so I usually code my proposals directly in HTML+CSS. Build on top of the open source XWiki platform.