Many organizations offer information about and assistance to the manufacturing technology industries.  Here are some of them:

American Gear Manufacturers' Association
Information on gear technology and a source of U.S. gear-related standards.

American Iron and Steel Institute
A source of information about the steel industry.

American Machine Tool Distributors' Association
Provides link for membership directory of members.

American Precision Museum
The largest collection of historically significant machine tools in America. The museum is located in Windsor, Vermont.

American Society for Testing and Materials
Resource for individual standards and technical publications.

American Society of Mechanical Engineers
Source for technical abstracts and news.

AMT - Central/Eastern Europe
AMT - The Association For Manufacturing Technology Central/Eastern Europe office website. 

AMT - China
AMT - The Association For Manufacturing Technology China office website. 

AMT - India
AMT - The Association For Manufacturing Technology India office website. 

AMT - Mexico
AMT - The Association For Manufacturing Technology Mexico office website. 

ASM International (formerly American Society for Metals)
Data on alloy properties.

Electronic Industries Alliance
Information on electronic standards using machine tool controls.

The Instrumentation, Systems and Automation Society
An in-depth "Web Resources" page provides useful links to many technical subjects.

Machinery Dealers National Association
Published the annual Buyer's Guide; a listing of used capital equipment.

Manufacturing Technology Information Analysis Center (MTIAC)
MTIAC is a Department of Defense (DoD) Information Analysis Center, sponsored by the Defence Technical Information Cetner (DTIC), and operated by Alion Science and Technology. MTIAC promotes the exchange of manufacturing technology information and supports DoD Manufacturing Technology (ManTech) program objectives. 

National Association of Manufacturers
Source of information about and services for manufacturing companies of all kinds.

National Center for Manufacturing Sciences
Membership organization providing industry news, opportunities for collaborative R&D, manufacturing data and related services.

National Coalition for Advanced Manufacturing
Membership organization providing information on manufacturing-related legislation and promoting skills standards.

National Fluid Power Association
Sources of hydraulic and pneumatic related standards.

National Institute for Metalworking Skills
Organization devoted to developing skills standards and certifications for the metalworking industry.

National Institute of Standards and Technology
An agency of the Department of Commerce, works with the industry to develop and apply technology, measurements and standards.

National Tooling & Machining Association
Member organization representing contract manufacturers - job shops

Precision Metalforming Association
Member organization representing the metalforming industry of North America.

Robotic Industries Association
Represents companies in the industrial robotics industries.

SkillsUSA
National organization serving high school and college students enrolled in technical, skilled and service occupations.

Society of Automotive Engineers
Source of various automotive product design related programs, as well as standards.

Society of Manufacturing Engineers
Manufacturing news and technical abstracts.

Society of the Plastics Industry
Resources and information for plastics industry trade association.

Tooling & Manufacturing Association
Membership organization representing Chicago-area companies engaged in precision metalworking, plastic molding and their supplier companies.

United States Cutting Tool Institute
National organization representing companies that produce cutting tools and accessories.