most prob neat image or noise ninja would do it. for budget ppl like me. I would do this in the photo editor
this is just a general command. You can apply despeckle to various channels and see the effect. Normally I'll convert to LAB and apply despeckle to the lightness channel then apply very light gaussian blur to the A and B channel.
The above technique works for CCD imagers like the D70 that produces "grainy" noise.
For CMOS/SuperCCD sensors that produces 'patchy' noise. It won't really work much.
This is just a general technique I use. Sometimes I'll apply to R,G or B channel.
For different types of pictures there are always short cuts.
If the picture has 1 subject and a very smooth and clean bg (shallow DOF) I'll just mask out the BG and apply guassian blur (to the BG).