PlanetData aims to establish a sustainable European community of researchers that supports organizations in exposing their data in new and useful ways. The ability to effectively and efficiently make sense out of the enormous amounts of data continuously published online, including data streams, (micro)blog posts, digital archives, eScience resources, public sector data sets, and the Linked Open Data Cloud, is a crucial ingredient for Europe's transition to a knowledge society. It allows businesses, governments, communities and individuals to take decisions in an informed manner, ensuring competitive advantages, and general welfare. Research will concentrate on three key challenges that need to be addressed for effective data exposure in a usable form at global scale. We will provide representations for stream-like data, and scalable techniques to publish, access and integrate such data sources on the Web. We will establish mechanisms to assess, record, and, where possible, improve the quality of data through repair. To further enhance the usefulness of data - in particular when it comes to the effectiveness of data processing and retrieval - we will define means to capture the context in which data is produced and understood - including space, time and social aspects. Finally, we will develop access control mechanisms - in order to attract exposure of certain types of valuable data sets, it is necessary to take proper account of its owner's concerns to maintain control and respect for privacy and provenance, while not hampering non-contentious use. We will test all of the above on a highly scalable data infrastructure, supporting relational, RDF, and stream processing, and on novel data sets exposed through the network, and derive best practices for data owners. By providing these key precursors, complemented by a comprehensive training, dissemination, standardization and networking program, we will enable and promote effective exposure of data at planetary scale.