I got really interested in the soroban at one point, and taught myself how to do basic arithmetic on it, with the ultimate goal of being able to do quick mental math. Unfortunately, I got bored after a while and never did achieve my ultimate objective and now don't really remember how to do it. It's one of those "use it or lose it" skills.

However, I do still have links to some of my favorite videos showing some really amazing soroban or flash anazn feats:

Soroban - All in the mind[1], Flash Anzan at the All-Japan National Soroban Championship 2012[2], and Mental Arithmetic World Champion - Flash Anzan[3]

There's an excellent, free book on it: Abaucs: Mystery of the Bead[4]

r/soroban and r/mentalmath are worth peeking in to.

I also really enjoyed reading a blog called Going Gaijin, written by a woman who took formal soroban classes in Japan.[5]

There are a lot of cheap, decent sorobans on amazon and ebay, if you want a physical device. I also found the "Simple Soroban" Android app to be useful for practice.

[1] - https://www.youtube.com/watch?v=Px_hvzYS3_Y

[2] - https://www.youtube.com/watch?v=7ktpme4xcoQ

[3] - https://www.youtube.com/watch?v=JawF0cv50Lk

[4] - http://totton.idirect.com/abacus/

[5] - http://goinggaijin.com/2014/04/28/392/