Numismatics, Greek & Roman

The International Numismatic Council was founded in 1927 and established as International Numismatic Commission affiliated to the the International Committee of Historical Sciences in 1934 to promote numismatics and related disciplines by facilitating cooperation among individuals and institutions in the field of numismatics and related disciplines. In 2009 the name was changed in International Numismatic Council/ Conseil international de numismatique.
Frpm their website

Founded in 1836 as The Numismatic Society of London, today’s Society is international in subject and membership. Its lectures and publications deal with Classical, Asian, Medieval and Modern coins, paper money, tokens and medals, and Fellows include scholars and enthusiasts from around the world.
From their website

Nomisma.org is a collaborative project to provide stable digital representations of numismatic concepts according to the principles of Linked Open Data.

Online Coins of the Roman Empire (OCRE), a joint project of the American Numismatic Society and the Institute for the Study of the Ancient World at New York University, is a revolutionary new tool designed to help in the identification, cataloging, and research of the rich and varied coinage of the Roman Empire. The project will ultimately record every published type of Roman Imperial Coinage from Augustus in 31 BC, until the death of Zeno in AD 491.
From their website

Numishare is an open source suite of applications for managing digital cultural heritage artifacts, with a particular focus on coins and medals. It is developed and maintained by the American Numismatic Society and employed for its online collection. The architecture of the application is built upon an XML foundation. Coins and medals are described in an XML adaptation of NUDS, the Numismatic Database Standard. Other artifacts are encoded in VRA Core 4.0. The adherence to common library/archive/museum standards and best practices ensures the long-term sustainability and curation of the data.
From their website

A great guide, written by: Daniel Gleich, for those just getting started.