MacFusion is the closest free solution so far. I think I got scared off by the comment that it wasn't quite the same as SFTP, which I understand as not being the same as FTP over SSH. I couldn't connect to any of my servers that don't support FTP (and instead support SFTP) using the sshfs option in MacFusion.
So I tried compiling instead, which I found to be involved only because, after installing MacFuse, I had to compile for pkg-config, gettext, glib, glib2 (which I had to get using MacPorts, which requires Xcode Developer Tools and X11), and sshfs. All of this compiling took about two hours. So yes, it wasn't quite the ideal technique for an end-user.