Blender 2.67 has just been released and there is already awesome new things added to the development version of Blender 2.68. Like this great new feature by MiikaH - smooth emitters for high resolution smoke and fire simulations!
This addition fixes one of the most annoying things of the smoke simulation in Blender - the blocky artifacts around the emitter. From now on, when you use the HiRes-option, the emitter will be perfectly smooth: