All the call information can be found on the new Participants Portal: http://ec.europa.eu/research/participants/portal/desktop/en/home.html.
An overview with all open calls can be found here: http://ec.europa.eu/research/participants/portal/desktop/en/opportunities/h2020/master_calls.html.
More information about Horizon 2020 can be found on the new HORIZON 2020 site of the EC: http://ec.europa.eu/programmes/horizon2020/.
The Horizon 2020 Work Programme 2014-15 sets out the funding opportunities under the different parts of the programme; all are being published on the Participant Portal http://ec.europa.eu/research/participants/portal/desktop/en/home.html. Each part describes the overall objectives, the respective calls, and the topics within each call. Each topic describes the challenge to be addressed, the scope of the activities to be carried out, and the expected impacts to be achieved. Compared with the Seventh Framework Programme (FP7), there are relatively fewer calls and topics. The Work Programme reflects the strong challenge-based approach of Horizon 2020, allowing applicants to have considerable freedom to come up with innovative solutions.