Burning Photoshop!
There's a whole bunch of plugins that can light a fire in Your images.. but none of them does it for free and most of them gives crappy results. As with so many other things in photoshop, Your much better of without the plugins! Here's a guide on how to make realistic fire.

This tutorial is a simplified version of Greg Vander Houwen's great fire tutorial which can be found at www.photoshoptechniques.com. I suggest that you take a look at his tutorial if you are a more experienced user of photoshop. His version also includes a quicktime instructional video, so if your ready for some more advanced fire effects go visit his site.

Here we go:

Run photoshop. Go to |file/new| or press |ctrl-n|. Make a new document that's about 300x400 pixels. Set the background to be white. Press |ok|.

Press |t| which is the shortcut for the font-tool. Press |d| with the font tool selected to make the font color black. Find a font that You like.. the best results come when choosing a bold font. I'm using Arial Black in this tutorial. Now, write the text that You want to set on fire.

Remember to leave some space for the flames!

Press |alt-ctrl-shift-n| to make a new layer. After You've done this, press |alt-ctrl-shift-e| to merge all visible layers to the new layer while retaining the layer hierarchy Now we need to rotate the layer 90°. Do this by pressing |edit|transform|90 ccw|.

Press |ctrl-i| to invert the colors.

After that, go to |filter|stylize|wind| and copy my settings from bellow:

Press |ok|.
Then You need to press |ctrl-f| to repeat the filter. Do this two times.

Rotate the layer back to it's initial position by going to |edit/transform/90 cw|. Then go to |filters/blur/gausian blur| and copy my settings from below:

Press |ok|.

Go to |image/adjust/hue-saturation| or Press |ctrl-u| and copy my settings:

Press |ok|.

Go to |filter/liquify| or press |shift-ctrl-x|. Select the upper left tool and find a fitting brush size. After this You need to draw the flames out from the image:

Make a copy of the layer by pulling it from the layer menu down to the new layer icon. After You've done this, go to |image/adjust/hue-saturation| and copy my settings:

Press |ok|.
Set layer mode to |overlay| in the layer mode drop down.

Now we need some glow to spice up the flames! Make a new layer |alt-ctrl-shift-n| and press |alt-ctrl-shift-e| to merge all visible layers onto the new layer. Set layer-mode to screen. Go to |filter/blur/gausian-blur| and copy my settings:

Press |ok|.
Spiffy aint it? =)

Congratulations!! You've made it all the way through the tutorial.