There are many many guitar string manufacturers, makes and brands around the world, but here's an overview of some of the most popular:

D’Addario

"The Players Choice"
Both electric and acoustic guitar strings are supplied in sets packaged within a single 'corrosion intercept' environmentally-friendly package. Individual strings are identified by the colour of the ball-end and a key to colours is supplied on the packaging.
See our home page for a great video of guitar strings being made in the D'Addario factory.
www.daddario.com

Dean Markley

"Every product the very best in its field"
With their headquarters in California and with their own manufacturing facility in Kalamazoo, Michigan, Dean Markley Strings - or DMS for short - manufacture a wide range of popular electric and acoustic guitar strings that are used and endorsed by a wide range of artistes, the most famous of which is probably the incredible guitarist that is Yngwie Malmsteen! (http://www.deanmarkley.com/EndArtists/YngwieMalmsteen.shtml)
Acoustic strings include Alchemy, Vintage and Blue Steel ranges, whereas electric strings include endorsed versions named after Yngwie Malmsteen, Jimi Hendrix and Floyd Rose among others. Floyd Rose "speedloader" strings are specially designed to be used with the incredible Speedloader Tremolo Bridge that enables you to change your strings and have them in tune in under a minute!
www.deanmarkley.com

DR Handmade Strings

"Born in NYC, wound up in New Jersey"
Founded by Mark Dronge, son of the Guild Guitars founder, DR Handmade Strings make a diverse range of acoustic, electric and bass guitar strings which, not unsurprisingly, the test on Guild guitars! DR believe in combining old-fashioned craftsmanship with modern materials to create strings that give the feel and tone that players want. Endorsing artistes include U2's Adam Clayton. Voted Number One in Bass Player magazine's 2008 Reader's Choice Awards.
www.drstrings.com

Dunlop

Heavy Metal Favourites
Dunlop electric guitar strings are made in California by Jim Dunlop, famous for the Cry Baby Wah-Wah pedal amonst other things. Bright, well balanced and punchy, these guitar strings are designed for extremely long life and provide low tension with minimum break-in time. Popular with Heavy Metal Artists like Zak Wylde
www.jimdunlop.com

Elixir

Hi-tech coated strings
In 1995 Elixir started experimenting with coating strings with PTFE. After much trial and error and analysis, prototypes were tried by over 5,000 guitarists and other musicians before Elixir final released their masterpieces. Today their NANOWEB and POLYWEB coated strings are used by guitar players worldwide. Not cheap to buy, but claimed to last 3-5 times longer than 'regular' strings!
www.elixirstrings.com

Ernie Ball

Probably the most famous brand of all

Ernie Ball invented the trademary 'Slinks' range of guitar strings back in the 1950s and built a world-wide brand known for it's wide choice of 'custom' gauge sets. The regular choice of millions of guitarists worldwide.
Read the Ernie Ball Biography.
>> Details of Ernie Ball Slinky range of electric guitar strings, including gauges.
www.ernieball.com

Fender

Iconic maker of the Tele and Strat
Fender invented an alternative to the ball end - the bullet end - especially for Fender guitars
www.fender.com

GHS

GHS Boomers
www.ghstrings.com

La Bella

America's largest string maker
E. & O. Mari, Inc., the maker of La Bella Strings, is one of America's oldest and largest manufacturers of fine strings for virtually every kind of stringed instrument including guitars. La Bella are one of the only companies in the world still making traditional, real gut strings for antique and Baroque guitars. Other materials used include three different types of nylon, Kevlar, copper, brass, bronze, silver, aluminum, in addition to numerous types of steel. Each string is created using a combination of tradition and technology. Sophisticated, computer controlled and automated string-winding machinery is used where applicable, but hand-winding is still used where it delivers the best results.
www.labella.com

Martin Guitar Strings

Acoustic favorites
A wide range of Bronze, Phosphor Bronze and Coated strings in every conceivable gauge and type. CF Martin & co are well known as makers of top quality acoustic guitars and their strings are made to the same high standard. Core and wrap wires must meet strict requirements to make the grade and Martin Strings are wound to precise specifications
www.martinguitar.com

Rotosound

As British as the Beatles

Famous for ROTO Color strings (ROTO Pinks, ROTO Yellows etc) developed in conjunction with some of the worlds top artists, these unique sets deliver a smooth powerful tone that lasts while other strings have long gone dead.
www.rotosound.co.uk

....more to come!