Links to other people's websitesThe online reference "par excellence" for everything calculator-related, and the online version of Martin's famous book is
Another very useful website is rechnerlexikon.de
John Wolff is a fellow collector and excellent technician, who documents his restorations meticulously. His website is a joy to behold for everyone who loves these little mechnical wonders.
Herbert Schneemann has a varied collection of antique mechanical calculators.
Walter Szrek is a collector of mechanical calculators in the US.
Stephan Weiss has a website full of interesting articles and original manuals for the use of many calculators.
Rick Furr is the reference where Curta calculators are concerned
...together with Jack Christensen
...and Jan Meyer.
Curta.li is a beautifully designed website with all sorts of rare and never-seen-before documentation and pictures of Herzstark's Curta. Highly recommended!
Valéry Monnier is a French collector of Thomas arithmometers, who has gone to great length to set up a database and collect all sorts of information on them. Since Valéry is a man of many interests, he also has a website on other 19th century calculators, which contains a lot of obscure and unknown machines. Very much worth a look!
Nico Baaijens is a Dutch collector of mechanical calculators.
Serguei Frolov documented the Russian calculator history - lots of machines here that are seldom found outside of the former USSR.
Kevin Odhner is the great-grandson (or at least family) of Wilgodt T. Odhner, and took up an interest in these iconic calculators.
The Swedish Typewriter Page contains a few tidbits on calculators as well, including the definitive visual reference on Odhner models.
Freddy Haeghens is a fellow Belgian collector.
Jay Goldman is a well-known US collector of mechanical calculators.
Detlev Bölter is one of the most talented restorers who has seen many rare and even unique machines pass through his workshop. Reading through his website is a true delight.
dr. Erhard Anthes was a professor (now emeritus) at Ludwigsburg University's Institut für Mathematik und Informatik, and creator of the MMM, the Mathematisches Maschinen Museum.
Christophe Méry is a French collector of mechanical calculators. He has recently built a site on the history of W.J. Wang is one of the rare Chinese collectors of mechanical calculators - his blog is unfortunately in Chinese.
Eduardo Guillem collects typewriters and calculators in Alicante, and has made this beautiful site.
Friedel Schmitt has a collection which is much larger and more varied than what is on his website!
Mark Glusker collects mainly electromechanical calculators, but did build a replica of Fowler's balanced ternary calculating machine. Very much worth a look! Also see Kevin Twomey's documentary on Mark's collection here.
Reinhold Rehbein is a well known German collector and restorer of technical antiques. He has some beautiful pictures of machines on his website.
Wilfried Denz is a very ambitious collector who collects everything related to calculating without electricity. A beautiful site with interesting pictures, and in full development.
Georgi Dalakov owns a beautiful site oriented to the inventors and their patents and inventions - all related to calculating aids and machines. Warmly recommended!
Kees Nagtegaal is yet another Dutch collector, mainly of small calculating aids, but his website contains a section on pinwheel calculators as well.
The Computarium is a small museum of calculation and informatics at the Lycée classique de Diekirch, in Luxemburg, and well worth a visit.
ANCMECA is the French association for old technical devices, their website hosts Michel Bardel's list.
The IFHB is the German Association for the Historic Office-world.