А ццц.learning-maya.com не канает? Там ведь ВСЕ основные вещи есть! Например, урок с падающими листьями - чем не сабж?
"... For this test, create a simple poly-leaf and let it instance the particles (to do that, just select the geometry (you don´t need to select the particles) and open the optionbox from the "Instancer"-command within the Particles-menu - the default-settings should be fine, just make sure that under "Particle Object to Instance" the right particles are selected - and finally hit create). Now the particles are replaced with the geometry...."