The World List of Cycads, produced under the auspices of the IUCN/SSC Cycad Specialist Group, has been selected as the taxonomic data provider for The Catalogue of Life (CoL). According to the CoL website:
The Catalogue of Life is the most comprehensive and authoritative global index of species currently available. It consists of a single integrated species checklist and taxonomic hierarchy. The Catalogue holds essential information on the names, relationships and distributions of over 1.5 million species.
A list of accepted Cycads on the Catalogue of Life can be found here.