There are several different types of animated smoke effects you can create in After Effects, and several ways to create them. I choose this tutorial because it was easy and the effect is effective.
Richard Lainhart, 2011. How to create smoke effects in After Effects. [online] macProVideo.com. Available at: <http://www.macprovideo.com/hub/after-effects/how-to-make-smoke-after-effects-effects> [Accessed 25 July 2012]
annitaki 