Open Data is data made available without restriction for re-use, with or without attribution, depending upon the host requirements.
Here you'll find a small selection of open data repositories in the sciences. Many more exist. For more extensive lists, see the links, below.
We also have a guide on Data Management. This guide is intended to support researchers who want to effectively manage their data. It is intended to help researchers to understand requirements from grant funding agencies for managing data and the research data life-cycle.