Fat Quarters Software and Electronics  
   Really slick magnetic field sensors. And the electronics to interface them.
   http://www.fatquarterssoftware.com/

Magmess Magnet  
   Over thirty years in magnetic field measuring and testing; products include gaussmeters, fluxmeters, and measuring coils
   http://www.magmess-ballanyi.de/en/index.htm

Forcefield  
   Powerful Neodymium and Ceramic magnets and other products, sold new and surplus and at wholesale prices. Site also has a FAQ for magnets and electromagnetism, and magnetic demonstration images.
   http://www.wondermagnets.com/

Bartington Instruments  
   Bartington Instruments manufacture fluxgate magnetometers, magnetic field sensors and magnetic susceptibility systems for soils and rocks
   http://www.bartington.com/

Stangenes Industries, Inc.  
   Transformers, current transformers, voltage dividers, electromagnets, X-ray power supplies, pulse forming networks.
   http://www.stangenes.com/

AMAC International Inc.  
   Manufactures advanced magnets, cryostats and SRF cavities. The company provides low cost equipment and a variety of services to scientific community of accelerators, superconductivity and cryogenics.
   http://www.AMACintl.com/

Group3 Technology Ltd.  
   Precision Magnetic Field measuring instruments, and fiber optically linked Distributed Control Systems.
   http://www.group3technology.com

Electronic Filters  
   Real-world signals contain wanted and unwanted information. Therefore, some kind of electronic filtering technique must separate the two before processing and analysis can begin.
   http://www.freqdev.com/filters.html

Books on Electromagnetics  
   Online bookstore for books on electromagnetics and relating subjects, links on the subject.
   http://www.electromagnetics.co.uk

Educational Magnets from Indigo Instruments  
   Neodymium rare earth magnets, steel bar magnets and horseshoe/U-shape magnets for science education, industry and magic.
   http://www.indigo.com/magnets/magnets.html

Hocking NDT Ltd.  
   Company specializes in eddy current non destructive testing (NDT). An overview of NDT is provided, including theory pages on electromagnetics and practical applications.
   http://www.hocking.com

Stefan Mayer Instruments  
   Fluxgate magnetometers, magnetic field compensation systems (active magnetic shielding), and magnetic permeability meters.
   http://www.stefan-mayer.com/

Space Cryomagnetics Ltd.  
   Company provides a complete service from design, through assembly, to installation and commissioning. The focus is on custom-built and special magnets, but the company also supplies standard cryogenic equipment and consultancy services.
   http://www.spacecryo.com

Spicer Consulting  
   Electron beams and electronic systems. Equipment for measuring and cancelling magnetic fields in the environment of electron microscopes.
   http://www.spicerconsulting.com

Kemo Filters  
   Kemo produce a wide range of electronic signal filters, from simple filter modules to complex computer controlled multi-channel systems with gain.
   http://www.kemo.com

Speake Sensors and Co Ltd  
   Manufacture and supply Magnetic Field Sensors, used by a series of ASICS (Application Specific Integrated Circuits) for applications such as gaussmeters, vehicle detectors, compasses, magnetometers and gradiometers.
   http://www.speakesensors.com/

Jandel Engineering  
   Manufacture probes for resistivity test measurement of semiconductors, silicon wafers and thin metal films. Based in Leighton Buzzard, UK.
   http://www.jandel.co.uk/

VS MicroAnalytical  
   Vacuum Systems for Micro Analysis is a manufacturer of photo-electron mass spectrometers capable of fast quantity non-destructive chemical mapping. Based in UK.
   http://vacsys.co.uk

Nippon Ryutsu System Ltd.  
   Company advertises 120dB high-performance shielding material for electromagnetic waves.
   http://www.venus.dti.ne.jp/~nrs/english/

Serviciencia  
   Company supplies instruments and service for several fields in science. Special expertise is in magnetic instruments and screening, as well as medical related devices. Based in Spain.
   http://www.serviciencia.es/home.htm

MetaMaterials  
   Electromagnetic complex materials with both negative real permittivity and permeability. The web site includes information and provides a forum for discussion.
   http://www.metamaterials.net

Antenna Systems  
   High efficiency wire antennas.
   http://dxantennas.com

EMproto  
   Professional engineering services in Ontario, Canada. Numerical electromagnetics prototypes and analysis of antennas, scatterers and coupled structures in support of system design, troubleshooting and compliance assessment.
   http://www.emproto.com/

Marine MT Instruments  
   Magneto Telluric instruments for marine geophysics can record high frequency data, combining magnetic field and electric field measurements. Located in Brest (France).
   http://www-sdt.univ-brest.fr/~deu/simbapub/

Magnet Enterprises International  
   MEI provides a broad spectrum of services that include design and manufacture of electromagnets for high energy physics, fusion research, hi-tech, medical, and other industrial applications.
   http://www.meimagnet.com/

National High Magnetic Field Laboratory at Florida State University  
   The NHMFL develops and operates high magnetic field facilities used for research in physics, biology, bioengineering, chemistry, geochemistry, biochemistry, materials science, and engineering.
   http://www.magnet.fsu.edu/

Integrity Design and Research Co.  
   High quality instrumentation and detectors for magnetic field AC,DC and for nuclear radiation (apha, gamma, and x-radiation) measurement.
   http://www.gaussmeter.info/

Custom Magnet Supplier  
   Supplier of magnets, specializing in custom magnet shapes and designs. Eagerly works with inventors, companies, universities, schools, and individuals worldwide.
   http://www.engconcepts.net/

MAGNICON  
   High performance SQUID electronics and laboratory amplifiers.
   http://www.magnicon.com

Gaussmeters and Hall Probes  
   Hirst Magnetic Instruments Ltd. manufactures a range of portable and handheld gaussmeters for measurement of magnetic flux densities.
   http://www.gaussmeter.co.uk

Caylar Magnetic Instruments  
   Caylar is a manufacturer of NMR and Hall effect gaussmeters (teslameters), magnetic field regulators in closed loop systems.
   http://www.caylar.net

Yuxiang Magnetic Material Co.  
   Produces hard ferrite, permanent, rare earth, NdFeb, Neodymium, SmCo, and AlNiCo magnets. Headquarters located in Xiamen, China.
   http://www.e-magnet.cn