The "
Methode de Batterie" series of books by Dante
Agostini are well known by drummers as a comprehensive method for the kit. Check out volume IV for a number pages of
polyrhythms that can also be used by other musicians. There are two part exercises that can be played between the hands. They start
progressively with 16
th and 8
th notes, and then explore 2 against 3, and 3 against 4. Although I have not reached the end yet, I have found this a very systematic and
practical method, which followed step by step helps to learn these
rhythms thoroughly. http://www.danteagostini.com/methodes/volumes.html