Hi,
I find Picture Cooler works well, it is a freeware Noise reduction program and the latest version has a plug-in for PS, I haven't played around with it to find out how it works yet.
I use CS2 and the noise reduction filter leaves a lot to be desired, I've used Neat Image and Noiseware but have found Picture Cooler works best for me.
* *http://denoiser.shorturl.com/