Avatar/LJ Icon Tutorial:
Written by Aly. Done in PS 7.0

LEVEL - HARD(er)/PRE-EXPERT

1:  Choose your image, and crop it to 100x100 pixels, and sharpen*


2: Copy your image, and set the blending option to Screen.



3: Copy this image, and set to Screen 50%.


4:  Open your Selective Color option. (Image >> Adjustments >> Selective Color...)
Set your Method to Absolute.


5: Now, follow these instructions (one thing important to remember about selective coloring is that the result is highly dependent upon your image. Mine happens to be very blue.):
Reds:
Cyan -100, Magenta +100, Yellow +100, Black +100
Yellows:
Repeat steps for Reds.
Neutrals:
Cyan 0, Magenta +27, Yellow +41, Black - 16.   (Ignore this step if your image is not heavy on the blue tinting.)


6: Open the Selective Color window again.


7: Follow these instructions:
Reds:
Cyan -50, Magenta +20, Yellow +40, Black +60
Yellows:
Cyan +15, Magenta -40, Yellow -100, Black -15.
Neutrals:
Cyan 0, Magenta -5, Yellow -3, Black 0.
 

8: Now place this grunge texture over your image and set it as Multiply, 100%. (Texture by myself)

9: Add some text etc. and you're done! 
Congrats!  Selective coloring ain't easy.  It takes a while to get used to. ;)

*Please remember that sharpening always depends upon the image you are using.