One of the most useful programs that I have found with regards to reducing noise in images is this little program: Neat Image. Utilizing it for reducing the noise in my imagery has been one of the saving of quite a few images that would be unuseable due to noise.
This program is reputedly one of the best noise-reduction programs on the market. As I am mostly utilizing this for personal use, I have opted at this point to use the free-ware demo program. Check them out at Neat Image.com. If you are planning to use this for commercial use, I would suggest that you purchase the program because it is probably one of the most effective anti-noise programs out there. You can see exactly what it has done in these two images that I took of the moon out at Iona Beach last Sunday.
Image without noise reduction:
image with Neat Image noise reduction:
Notice how the second image looks much smoother and crisper. The image above that looks grainy and pixellated. Now note this doesn't do anything for an image that is small in size. For best effect, you have to use it on an original size image (anything from 1500px width up).
I would have to say Neat Image has saved a number of my images that I've taken at dusk, mainly because my camera has pushed high-ISO (High-ISO in a DX frame camera will be useable but grainy straight from the camera). This program is essential for any photographer.