S... Luthiers (21st C.)

Founded in 2005 and based in Seto City, Aichi Prefecture, he learned to make Ukuleles working for Seiichi Nakanishi at the Nakanishi Musical Works starting in 1996, (before this he was and international triathlete who became interested in the Ukulele while competing in Hawaii). He makes Mini, (including a 14 fret long necked Mini that puts it back into the Soprano scale), 12 and 14 fret Soprano, Concert and Tenor scale Ukuleles with Concert being his prefered scale. I have also seen Concert scale Banjoleles made by him along with Concert scale Lili'u's and Guitaleles. Having learned to copy Martins at Nakanishi Musical Works he still likes to do this but he also copies Gibson Ukuleles too. He usually stamps the back of his headstocks and inside the soundhole with Shiihara Ukulele Factory and often uses a very narrow S as a logo, but he also does inlaid headstock fronts and sometimes inlaid fret markers; again sometimes only the twelfth fret marker sometimes all of them. 

He learned to make instruments at the Robert-Venn School Of Luthiery in the USA in 1980. He started his business in 1982 making all sorts of fretted instruments including Guitars and Ukuleles. He is currently based in Hachiouji, Tokyo and his designs range from the fairly traditional to the quite imaginative, with very much a "what if?" attitude
This is a different person to Takahiro Shimojima.

Takahiro Shimojima uses the branding Saiunkoubou, (the name apparently means Iridescent Clouds Stringed Instruments). He is a luthier who makes Guitars and Ukuleles with a very distinctive tuning peg arrangement. I think his workshop is in Minamiichiban, Yamagata Japan, he has been in business since before 2008
This is a different person to Takahiro Shimo

From Managua, Nicaragua he is known more for Classical Guitars, (where on some specialist forums there are questions about the quality?), but has made other instruments too, including Ukuleles.

He is quite a prolific luthier from Brazil. Unusually for a Brazilian luthier he seems to specialise in Ukuleles, making Soprano Supersoprano, Concert and occasionally Tenor scale instruments and has been doing so since before 2010 He has also taught at least one course on luthiery.

Goat Rock Ukuleles is the brand name used by Sebastopol, CA. luthier Michael F Smith. He has worked as a cabinet maker, finish carpenter and luthier all his working life and builds Ukuleles in small batches, often using recycled wood. He makes Concert and Tenor scale instruments with additional stringing as a custom option. He includes fine inlay work to his Ukuleles with a rooster's head as a default motif on his headstocks, (unless you choose a slotted headstock)

From Vancouver Island British Columbia, Don Stawski retired from lutheiry in 2008. Before this he made triangular acoustics in Soprano, Concert and Tenor based on the designs of Doane and solid electric travel Sopranos.

He started out as an apprentice under Tak Sakashita and then, (possibly after he died?) when to Mexico to study nylon strung instruments under Boaz Elkayam. Having finished in Mexico he came back to Japan and settled in Nagano and started working, (or maybe was an apprentice again?), for Eiichi Sumi. After more than 10 years at the Sumi workshop he now produces instruments under his own name, specialising in Flamenco Guitars but making Ukuleles as well. I'm not sure if he still works for Sumi too or is now totally independent?

Michael Sussman is from Kauai, Hawaii and uses Anahola as his branding. He has been making stringed instruments since the 1970's and his catalogue includes a couple of models of larger scale Ukulele along with Guitars and Violins. He is fond of taro leaf shaped epaulette and other side based sound holes in his designs