Network slicing is one of the key enablers to provide the required flexibility and to realize the service-oriented vision toward fifth generation (5G) mobile networks. In that sense, virtualization, softwarization, and disaggregation are core concepts to accommodate the requirements of an end-to-end (E2E) service to be either isolated, shared, or customized. They lay the foundation for a multi-service and multi-tenant architecture, and are realized by applying the principles of software-defined networking (SDN), network function virtualization (NFV), and cloud computing to the mobile networks. Research on these principles requires agile and flexible platforms that offer a wide range of real-world experimentations over different domains to open up innovations in 5G. To this end, we present Mosaic5G, a community-led consortium for sharing platforms, providing a number of software components, namely FlexRAN, LL-MEC, JOX and Store, spanning application, management, control and user plane on top of OpenAirInterface (OAI) platform. Finally, we show several use cases of Mosaic5G corresponding to widely-mentioned 5G research directions.