The particle generator is now a powerful enhancement to Carrara. I'm not aware of any really good tutorials on it yet, however. Most of what I know comes from directly working with it or adapting tutorials that I've come across for some other software like Maya. Sophisticated particle effects are processor intensive (which is true for any software using particles) While Carrara can do a bunch with particles, it's only advisable if you've got a system that's up to the task or a little extra time on you hands to let your computer chew on the work for awhile. ;) The most stunning effects can be created by mapping movies to the particles themselves - really fun stuff.