afp548.com published my article on how to replace the Apple-supplied FTP server with ProFTPd, with authentication through users and groups kept in MySQL instead of NetInfo or a simple passwd file. This is a nice tip if you're looking to serve up a lot of different users on a system without wanting them to be able to login via SSH and such. Read "ProFTPd, for the pro?" for the how-to.
[Editor's note: The article discusses the installation on OS X Server; I don't know for sure, but I suspect it would work as described for OS X Client as well.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021213120417434