Please find here an overview on GFZ data systems, e. g. IGS, ICGEM, ILRS, EMEC, Satellite Data, GEOFON.
KomFor is the link between research and community based data facilities, libraries and journals collaborating to improve the quality and availability of research data in the earth sciences. You can search for research data within various projects and data centers (e.g. PANGAEA, GFZ, WDCC).
DataCite an important partner for DOI allocation for research data. In collaboration with data centres, DataCite is developing a technical infrastructure to facilitate DOI registration and to offer additional services for access to research data, their citing and retrieval.
re3data.org - Registry of Research Data Repositories.
The web-based registry covers research data repositories (after specific selection criteria) from different academic disciplines and provides an current overview on international data collections.