Shareware

Aros Magic Checkers
Also called Draughts, this version of the classic game of Checkers can be played against a computer opponent or a friend. Observes the standard tournament rules of US/Britain. [Win 95/98/Me/NT/2000]
http://www.arosmagic.com/Checkers/default.htm

Atlant Software
Russian Checkers is played on the dark squares only of a standard checkerboard. Support for Russian, Hungarian, Portuguese, and Spanish languages. [Win 95/98/Me/NT/2000]
http://www.atlantsoft.com/

Jean-Bernard Alemanni's checkers programs
Checkers programs playing many different variations (English/American, Brazilian, pool checkers, Spanish, international, Canadian, Shashki, Poddavki, Italian) with a 3D-look board. Shareware.
http://pagesperso-orange.fr/alemanni/

Serge Startsev
Four checkers games for download which play English/American, Prussian, international and Brazilian checkers, respectively. Shareware.
http://www.gambler.ru/plus/main.html