"Noise Ninja":http://www.picturecode.com/ and "Neat Image":http://neatimage.com get frequent mentions from the top photography sites for reducing "digital noise" Another often used tool is "DxO":http://dxo.com which corrects the imperfections of particular lenses digitally. They have a computer model for popular pro lenses and thus can correct lense problems. Pretty amazing really what you can do with digital post processing now.
What they do is look through the digital image for the random sparkles and things that the sensors generate and remove them. Pretty amazing.
Neat is $59 for the 16-bit Pro version and and runs as a Photoshop plugin or standalone. Noise Ninja Pro if $80 for both as well or $60 if you are a student. There are also 8-bit versions for amateur cameras. Ninja uses specialized profiles for specific cameras and scanners