Reynolds is a British company known for their 853 tubing, which gets harder and stronger after welding or brazing. They're also just starting to get into carbon fiber, aluminum, and titanium. You can order tubing directly from their British office.
Columbus is an Italian company that is probably the biggest, most diverse company around. In addition to standard steel tubesets, they make stainless steel and aerodynamic tubesets. They also offerer aluminum and titanium tubes, as well as a new super lightweight steel tubeset named Foco. You can get their stuff from Nova Cycles, Mr. Bringheli, or from Ceeway.
Deddaciai is an new Italian company that makes really great tubing. I am using their Zero Uno tubeset for my new road racing frame in progress (see below). Tubesets available from Mr. Bringheli
Vitus is a French company that made some nice steel tubing, but are more well known for they're aluminum bikes. Few people build with it here in the U.S. anymore, except for Harry Havnoonian and maybe Rivendell. Last I heard, Vitus was halting steel tubing production in order to focus on aluminum bikes.
Carpenter Technological Corporation makes a new super-stong steel alloy called AerMet 100, but it is exceedingly hard to get ahold of. In addition, few people build with it.
Easton is an American company that makes aluminum tubing. They've got some fantastic new tubing that uses Scandium to increase strength so that smaller diameter tubes can be used.
Alcoa is another American company that makes aluminum tubing, most notably for Saeco/Cannondale's pro road team. Unfortunately, they don't sell tubesets to individuals.
Henry James sells True Temper tubing, some of the best lugs around, frameparts, brazing rod, flux, jigs, alignment tables, etc. Pretty much everything you need to build a frame.
Joe Bringheli imports Dedacciai and Columbus tubesets, as well as many investment cast lugs and other frame parts. He also sells a wide range of jigs and cutters.
Nova Cycles is the major distributor for frame parts, lugs, Columbus tubing, and other things. Many builders use them.
Nova Cycles Supply
4111 Citrus Ave., #8
Rocklin, CA 95677
Quality Bicycle Products is a bicycle component wholesaler with whom many local bike shops have an account. They also sell True Temper tubing, lugs, and other frame parts.
Ceeway is a British distributor of tubing, lugs, frameparts, etc. They have tons and tons of lug styles.
Tecnociclo is an Italian company that makes dropouts and other frame parts in aluminum, steel, and titanium.
Long Shen is a Taiwanese company that makes lugs and dropouts.
Kinesis is a Taiwanese company that makes dropouts and other frame parts.
3Rensho (linked here via Makino cycle factory) is a Japanese company that makes some very cool lugs and frameparts, as well as complete frames. They specialize in track, but more specifically Keirin frames. Right now I don't think they're lugs are available for purchase in the US though.
Marchetti is an Italian company that makes jigs and other supplies. Very expensive.
Bike Machinery is another Italian company that makes jigs and other equipment.
Anvil Bikeworks sells frame jigs, fork benders, and other fixtures.
Renaissance Cycles is an internet store that sells Cyclus framebuilding tools. Good quality, and less expensive then other tool makers.
United Bicycle Institute distributes frame parts from Arctos and Paragon machine companies. Parts available in both steel and titanium.
Click here for a few photos of the framebuilding process. New photos of my metal fork building jig.
There are many framebuilders out there that really produce fine frames, pieces of artwork. The following list is only a small representation of them. Looking at their frames is usually a good way to get ideas for what you want your own frame to look like.
Framebuilder's Mailing List is an e-mail-based framebuilding bulletin that you can subscribe to. Lots of useful information passes through this new forum.
Stephanie Monfrey's web page has a lot of useful framebuilding info, especially regarding jigs and other fixtures.
The Bike Forest is a bicycle shop whose web page has CAD programs that allow you to design your frame geometry on-line.
Tim Paterek is a professional framebuilder who sells plans for frame jigs. He also has computer programs which you can download for free which calculate the dimensions for your frame.
Tensile strengths can be a great help in choosing the right tubeset for a frame.
Josh Putnam has a page describing the steel frame that he built himself. He's also the one that set up the Framebuilder's mailing list.
Damon Rinard has a page describing how he built a frame out of carbon fiber. He's also got a program that plots the exact shape of a specified tube miter.
Fresh Frame has a lot of pictures of frames they've painted, and is a good source of ideas.
Gingery's pipe bender is a book that tells how to build a cheap pipe bender. Very handy for bending forkblades.
Biking.com Biking.com has links to just about any bike topic imaginable. A great resource.
Almost all of this info on this page came from a framebuilding page at Dartmouth (ref)