GroupNames.org is a database, under construction, of names, extensions, properties and character tables of finite groups of small order. Currently, it includes all 16309 finite groups that have order ≤500 and not 256 or 384.
I would like to thank Sam Chow, Henri Johnston, David Roe, Xavier Roulleau, Urs Schreiber, and Karl Syassen for additions, corrections and suggestions.
Questions/comments to Tim Dokchitser.