You can use the following URL if you are running sshd on your mac "sftp://macip/path/to/knoppix/user/readable/directory" in kde's konqueror Location bar. You can also use sftp on the command line.

But it sounds like what you want to do is create your shares with SWAT the web front end to Samba on Knoppix then start samba ("/etc/init.d/samba start" in the root console). On Mac OS X you may be able to create shares that are accesible to Windows machines from the front end. If not, you can always install samba on Mac OS X. There are packages that work with the installer on Mac OS X available on the internet. Just search on Google. Mac OS X lets you browse SMB shares. You can use smb://hostname/sharename/path in Konqueror on the Knoppix side.

For a quick and dirty read-only share method. Do a web share on the Mac OS X side. You can do a web share on the Knoppix side by right clicking on a directory and bringing up the properties dialog and going to the sharing tab and selecting share.