Fire effect with CSS3
Each shadow moves in the Y axis with a linear function and in the X axis with a cosine function. Pretty simple, but effective.
Update: I’ve added some randomisation to the algorithm, as well as an individual animation to each of the letters (which, as a drawback, makes the effect run less smooth). I’ve also added a fourth shadow in dark yellow. You can freely use the code by keeping the mention to this site and my name on it.