CBC News: Counterfeit Money: Report on Canada's counterfeit money problem.
Currencies of the World: List of currencies used in various countries.
Currency Boards and Dollarization: Information about currency boards, their history, how they work and understanding them.
Grandfather Foreign Exchange Report: Showing in picture form the long-term trends of the US dollar vs major competitors, with discussion on implications and policy.
S-WoPEc: Economic Structure and the Decision to Adopt a Common Currency: Extensively examines the question of whether given countries should adopt a common currency like the Euro
Transaction Net: How Money Systems Work: Overviews of how various currency (money) systems work, featuring a glossary and chart comparing the features of different systems.