Noise Ninja and other noise reduction sofware

I tested my Digital Rebel XT in low light levels, using a greenish wall as a background. I found ISO 400 went pretty well, but 800 and 1600 were pretty awful. I didn't try the trick of transforming the images to black and white, but I'm also lining up some noise reduction software to try:

• Noise Ninja: Used by many photojournalists.
• Neat Image: Cheaper.
  
• AbsoluteDeNoiser: Free

Graphic Converter also does some noise reduction. This review page looks very interesting.