GREYCSTORATION is a free “denoiser” for images. From what I’ve heard, it’s better than many of it’s competitors that cost $$$, and you can’t beat it’s price.
From the website:
GREYCSTORATION is an image regularization algorithm which processes an image by locally removing small variations of pixel intensities while preserving significant global image features, such as sharp edges and corners. The most direct application of image regularization is denoising. By extension, it can also be used to inpaint or resize images.