Sony Sound Forge or Adobe Audition. They are not cheap, but their noise reduction works well for removing noise. Remember though, you cannot polish a turd into a diamond... That is, if the recording is real noisy, you may find it difficult to get all of the noise out.
I haven't tried it yet, but there is a new version of Audacity out. I think it also has a noise reduction plug-in.
What ever you decide to do, don't go overboard on noise reduction. Doing multiple passes may be better than trying 100% in 1 pass.