There are some editors for raw images running on Linux (Dark Table, Raw Therapee, Bibble, ...). What about their skills at reducing digital noise? I'm interested in quality of the result and also in the CPU time required for the operation.
For me the Gimp plugin Wavelet Denoise showed best results mainly because of the option to manually adapt settings to your needs.
While i do not know the quality or the time taken you should try ufraw it is avaliable as a gimp plugin and as standalone software as well.
ADD by Spanky: ufraw is very flexible, for a wide range of cameras, and can be used by eye, with your cameras, ufraw color profile, or you can make one(or many) per camera. That give you instant results. The curves, which can also be loaded, and customized, are like D-Lighting (local contrasts) an more.
My point is, ufraw does not do the best NR, so I leave that off, and do it elsewhere, like Gimp. However, by shooting doing Raw, you will eliminate JPEG artifact noise. ufraw, is for quickly doing all 16-bit, light adjustments, when needed. Don't let its many options, through you. Read the ufraw web site.