American Contract Bridge League -- A huge site with resources for beginners through experts. Some interesting areas to check out include:
ACBL Member area -- Check your masterpoints online.
Tournaments -- Calendars and results from sectional, regional and national tournaments.
Convention cards -- Complete instructions on how to fill out your partnership's convention card.
Bridge laws -- American edition of the Laws of Duplicate Contract Bridge.
Alert procedure -- Detailed instructions and explanations on how to use the alert system.
Duplicate clubs -- Find a duplicate game in your hometown in this list of ACBL clubs in the U.S. and Canada.
Ecats Bridge -- News on international tournaments, laws and appeals, plus a good selection of articles and other interesting bridge features. Maintained by Anna Gudge and Mark Newton of the U.K.
Standard American Yellow Card -- Detailed explanations of conventions used in the "SAYC" system, which is popular among players in online bridge clubs.
How to matchpoint -- A step-by-step guide from Baron Barclay Bridge Supplies on how to figure matchpoints from traveling score slips and interpret the results on recap sheets.
Duplicate movements -- from Baron Barclay. Also available are Alex Groner's instructions for setting up a rainbow individual movement.
Duplicate scoring chart
Online bridge clubs -- Links to Bridgebase Online and other clubs where you can play duplicate bridge on the Internet.