Harris Cyclery:Articles about Bicycle Repair by Sheldon "Fixit" Brown
Ask the Mechanic: Andy the Mechanic, AKA Andy Wallen, fields technical and bicycle fix-it questions.
Bicycle Maintenance Guide: Summary of what an experienced cyclist has learned over the years.
Bicycle Maintenance Guide and Riding Tips: Contains maintenance tips and tutorials categorized by topic.
Bicycle Repair: A Free Internet Presentation That Shows You How To Fix Bikes
Bicycling Maintenance & Technical Books: Repair, maintenance, frame & wheel building.
BikeForums.net: Bicycle Mechanics: Topics include bicycle maintenance, repair and common issues and fixes.
BikeWebSite: Step-by-step guides for bicycle tune-up and repair. A comprehensive, illustrated, online bicycle repair manual.
Chain-Suck in a Nutshell: Chain-Suck binds chains onto the teeth of chain-rings, and brings pedalling to an abrupt stop. Find out why, and how to resolve the problem.
CyberCycle: Repair Shop Notes
FAQ from rec.bicycles.tech: "Frequently Asked Questions" list from the rec.bicycles.tech newsgroup. Valuable answers that give more details than most sources.
GeRZ Bicycle Gear Tables: Learn to check and evaluate bicycle gear ratios to improve the efficiency of your road or off-road bike -- includes both 27" and 26" gear charts.
Home made cheap bright light: Detail of my experience making a 20W 12V 20 degree headlight for my bicycle commute.
HPV Drivetrain Analyzer: Drivetrain evaluator for bicycles, tricycles and other HPV's that use chains, sprockets, geared cranks and hubs with 1:1 power transfer to environment, ie wheels rather than screws.
Mountain Bike Repair: Step-by-step bike tuneup and repair with color photos.
ProMechanics.com: USA Cycling's advisory board for bicycle mechanics provides this site on how to become or locate professional race mechanics. Also, includes resources for the mechanic.
Sturmey Archer SW Hubs: Hints and tips for maintenance and repair of the "silent" Sturmey Archer hub.
United Bicycle Institute Technical Forum: Post questions and get answers. Also, provides search engine that researches archived postings.