FTP4ALL is a free, open source FTP server implementation for the UNIX platform.
FTP4ALL was designed to require no superuser privileges. The advantages are
that FTP4ALL cannot be exploited to gain root access on a machine. And second,
any user on a UNIX box can run this server. It does not use the default user
database (/etc/passwd or NIS or whatever), or the UNIX file and directory
permissions. Instead, FTP4ALL sets up its own user and group database and
file and directory permission system. 

Those and other features like user upload and download ratios, IP checks,
bandwidth limit, transfer statistics make FTP4ALL a good choice for running
a private, specialised FTP site.

WWW: http://www.ftp4all.de/