The purpose of Data.gov is to increase public access to high value, machine readable datasets generated by the Executive Branch of the Federal Government. Data.gov provides descriptions of the Federal datasets (metadata), information about how to access the datasets, and tools that leverage government datasets.
GenBank is the NIH's genetic sequence database, an annotated collection of all publicly available DNA sequences. It is designed to provide and encourage access within the scientific community to the most up to date and comprehensive DNA sequence information.
The most respected scientific reference in the world, the CRC Handbook of Chemistry and Physics is an authoritative resource consisting of tables of data and current international recommendations on nomenclature, symbols, and units. Available online and in print.
The Durham High Energy Physics Database (HEPData) is a unique open-access repository for scattering data from experimental particle physics. It currently comprises the data points from plots and tables related to several thousand publications including those from the Large Hadron Collider (LHC).
SHARE is a higher education initiative whose mission is to maximize research impact by making a comprehensive inventory of research widely discoverable, accessible, and reusable. You can limit your search to "Data Set.".
The Dryad Digital Repository is a curated resource that makes the data underlying scientific publications discoverable, freely reusable, and citable. Dryad provides a general-purpose home for a wide diversity of datatypes.