World
- World Currency Gallery
http://www.banknotes.com/images.htm
displaying many thousands of images of bank notes from all around the world
U.S.
- Historical American Currency Exhibit
http://www.frbsf.org/currency/bills.html
from Independence to contemporary, finely broken down categories of historical currency of hundreds of times and regions.
Britain
- Britain Banknotes Virtual Tour
http://www.bankofengland.co.uk/banknotes/virtualtour/virtual_tour.htm
Bank of England banknotes: 5 pounds, 10 pounds, 20 pounds, and 50 pounds; Security features, design features, and and video.