Very simple and nice :)




Creat new BLACK document




Get good set of grunge brushes. Of course you can use one, like this: http://rapidshare.de/files/13168612/crazymind_brushes.abr.html
But if you will mix few sets it will looks better.




Use small sizes of brushes (~50) and draw flame-alike shape:

Color Balance

Click
Layer>New Adjustment Layer>Color Balance
and set values to:
Shadows: 0 0 0
Midtones: +100; -39; -97
Highlights: +93; +1; -35

Voila:

and 2nd version:

Hint

If u see too bright or too dark areas, use Burn and Dodge tools ;)