Online catalogs and databases
Coins and paper money
Numista
https://en.numista.com/
Internet catalog for world coins and paper money. Includes prices as well.
Sixbid Numismatic Auctions Archives
https://sixbid-coin-archive.com/
Numismatic auction archive displaying realized auction prices.
Coins
Coinage of the Roman Republic
http://numismatics.org/crro/
Online catalog for Roman Republican coins.
Online Coins of the Roman Empire
https://numismatics.org/ocre/
Online catalog of Roman Empire coins.
Sylloge Nummorum Graecorum
http://www.sylloge-nummorum-graecorum.org/
Internet catalog for ancient Greek coins.
World Coin Price Guide
https://www.ngccoin.com/price-guide/world/
Price guide to world coins published by the Numismatic Guaranty Company.
USA Coin Book
https://www.usacoinbook.com/
Internet catalog and price guide for US coins.
Paper money
Banknote Museum
https://banknote.ws/
World paper money catalog on the internet.
World Paper Money Price Guide
https://www.ngccoin.com/price-guide/world/
Price guide for world paper money published by Paper Money Guaranty.
Web catalog of dinars
http://dinar.notafilija.com/
Online catalog for paper money of Serbia and Yugoslavia.
Facebook groups
NumizmatikaNET – numismatics and phaleristics
https://www.facebook.com/groups/numizmatikanet
Buy, sell and exchange – coins, banknotes, decorations and badges
https://www.facebook.com/groups/kovanice.novcanice.odlikovanja.znacke
Numismatics
https://www.facebook.com/groups/390770595671388/
Dubrovnik currency – Coins of Ragusa
https://www.facebook.com/groups/1992159704397413
Numismatics Croatia
https://www.facebook.com/groups/390770595671388/
Old and new coins and banknotes
https://www.facebook.com/groups/465630283538758/
Coins of the World
https://www.facebook.com/groups/221281545076315
Notaphily Serbia
https://www.facebook.com/groups/3651450995177545