Bridge Bidding Guide:Look-up tables for bridge bidding, with the most common conventions used in "Standard American" bidding, by Richard Pavlicek.
Aggressive Bidding Foundation: Proposes an approach based on a math model over computer analysis. Provides famous pairs systems, an exposition of the theory and a bidding machine.
An Unassuming Club: A bidding system invented by Donald A. Varvel of Mountain View, CA, USA. It is based on an ambiguous 1 club opening, associated with 5-card majors, weak no trumps, and weak 2s.
An Unassuming Club: Presentation of a variant of the Polish Club system.
B-M Precision: Detailed presentation of a variation of the system.
Bidding by Design: Proposes articles on bidding system theory and offers examples for download. Free system design software available for download.
Bidding Guide: Introduction to standard American bidding.
Bidding Order Shows Strength (BOSS): Describes a system where priority is given to the strenght of the partnership hands.
Bidding Quest: Practice bidding on prepared deals with scores. Compare and check how other pairs have bid same boards. Try bidding competition with anonymous partner.
Brazilian Bridge: Presention of the Carioca Club and other conventions, links.
Bridge Conventions: Provides an encyclopaedia of conventions, systems and treatments.
Bridge Files: Provides overview of different systems, a list of conventions and information about the game. Free registration required.
Bridge Guys: Lists and defines a large number of systems and conventions.
Bridge is it: Concerned with bridge bidding systems, especially CLONE, based on a forcing weak/strong 1 club opening. Also features links to other bridge resources, particularly on bidding systems. Bilingual site (English/Norwegian).
Bridge World Standard: Description of a bridge bidding system based on the preferences of leading players, and aimed at the needs of occasional partnerships. Some characteristics: 5-card major opening, strong no-trump, artificial strong two-club opening, weak 2s in the other suits, and inverted minors.
Caliper: Bidding system from Norway based on a Big Diamond relay sequence.
Colonial Acol and LISA: Presentation of two bidding systems, one a US adaptation of the British Acol system, the other a modification of Standard American.
Contract Bridge Culbertson System: Contract bridge bidding, as developed by Culbertson. Culbertson's survey of good playing techniques is also included.
Conventions: Survey of a large number of commonly used bridge bidding conventions and bidding systems.
Coyot's 2/1 Game Force: Detailed presentation of this american system.
Inquiry 2/1 GF: Online book prensenting the author's variation of this popular north american system.
Key Lime Precision: Modified version of the Precision Forcing 1Club bidding system, with many transfer responses.
M.A.F. - The Ultimate Bridge Bidding System: A scientific bidding system from the Netherlands (5-card majors and different two-suiter openings). Bilingual site gives information in English and Dutch.
Neill, Daniel: Proposes bidding notes to download for many systems, conventions and treatments.
Pekiner, YAlçin: Proposes a collection of articles, tests and free software. English and Turkish.
Polish Standard 2000: Description of the Polish Club bidding system, with different variants.
Precision Bidding System: Detailed description of the Precision Bidding System (strong 1 club opening, with 16+ points), as modified by one partnership.
Precision Two-over-One: Presents an overview of a system mixing a strong club with standard methods.
REGRESsion: Modification of the bidding system Regres, based on frequent openings with weak hands and opening passes with strong hands.
SA-YC Simplified: This bidding system is a simplified version (as played on OKBridge) of the Standard Yellow Card (SA-YC) system of the ACBL (American Contract Bridge League). Its essential features include the strong no-trump, 5-card major and weak 2 openings.
The Blue Team Club System: Description of a complex bidding system invented in Italy. A major part of the information is in downloadable files only. Bilingual site (Italian/English).
The Chilli Bidding System: Gives priority to simplicity and universality of rules.
The Diamond Major: Forcing club, 5-card major, medium notrump system.
The L System: An original bridge bidding system presented by Hong Liu, based on very light openings.
Zar Points: Aggressive hand evaluation and bidding based on distribution, controls, and hcp. Presents the Zar Bid Machine.