Wikiwijs is a national open educational resources (OER) initiative in the Netherlands launched in December 2008. It aims to stimulate the development and use of OERs, improve education quality, and support teacher professionalization. Wikiwijs provides an OER repository, a referatory of digital resources, and tools for teachers to develop and use learning materials. All OERs in the repository must be published under Creative Commons licenses. Quality is ensured through peer review, ratings, and involvement of quality mark organizations.