I was having a play with the smoke and fire simulator over the past few days - but unfortunately it doesn’t work in cycles yet. I started looking around for some compositing tutorials - but whilst doing so, hit on another idea (one used in gaming).
Render out the smoke/fire as an image with alpha channel - then apply this as a texture to one or more planes in your cycles scene. By applying the correct materials to this plane (i.e. combining emission, transparency, alpha etc) - you can make the fire give off light and the smoke will cast shadows.
Whilst its not as good as true volumetric smoke in cycles - it might work quite well for simple scenes. Here is a quick and dirty test scene (obviously with more tweaking - it could probably look much better). I have also given the node setup for the material.
Next step is to try animating this method by rendering an colour and alpha pass in BI as an AVI - then applying the movie as a texture instead of an image.