The JewishGen Ukraine Special Interest Group maintains a Volhynia page that includes resources on Shumsk and its region.
JewishGen's Shumsk-related resources may be found here.
The Kremenets Shtetl CO-OP has many resources of great value to Shumsk researchers. Shumsk was one of the towns in the Kremenets District, and the CO-OP site has many relevant resources. You can dig deeper through their research page.
For people doing genealogical research, JRI-Poland offers an invaluable searchable database of
indexes to Jewish records of Poland, including many for Shumsk. You can
begin your search here.