I am going to say something that I habitually do not – except in those rarest of emergencies whereby there’s a shot at some make-up sex (usually with myself) – – – I’m sorry.
UPDATE: This tutorial is for the cavemen still using the Blender 2.49 series. Please, upgrade to 2.7 already! It’s SOOOO much better!!
And since 2.49 and 2.5 handle this topic differently, here’s the tutorial for 2.5 from Blendercookie.com. For 2.49 users, continue reading.