The Service Oriented Architecture (SOA) is increasingly adopted by industry as a paradigm for building distributed software applications. Yet, the SOA has currently several serious limitations and many crucial service issues are not addressed, including, for example, how to establish, monitor and enforce quality in an end-to-end fashion, as well as how to build service-based applications that proactively adapt to dynamically changing requirements and context conditions. This paper provides an overview of the service research challenges identified in S-Cube, the European Network of Excellence on Software Services and Systems. S-Cube strives to address those challenges by bringing together researchers from leading research institutions across diverse disciplines. The S-Cube researchers are joining their competences to develop foundations and theories, as well as novel mechanisms, techniques and methods for service-based applications, thereby enabling the future Internet of Services.