Joel Adams Shows How to Create Amazing Looking Cumulus Clouds in Blender.
Iridesium posts another tutorial that shows how you can create beautiful cumulus clouds using Blender. You might think that you need to work a lot with the smoke simulator or another dynamics drive tool to get the look that you need, and that is just not the case. Adams creates the clouds out of geometry, using a base shape of polygons which is then distorted by deformers into something more cloud-like.
Working this way makes it easy to art-direct the exact shape of the clouds that you need. Once the form is defined, it is just a matter of creating a volumetric scatter shader for the object giving it that puffy cumulus cloud look.