I've been toying with using noweb for some miscellaneous coding projects of late. I personally prefer Asciidoc over other formats supported as backends for noweb, including LaTeX and HTML, so I wrote a backend for it. A copy of my patchset can be found at:

http://www.mad-computer-scientist.com/files/toasciidoc.patch

The archive contains patches against the 2.11b release (current, as of this writing). Drop me a line if you have any questions or comments.