ProFTPD: The Professional FTP Daemon
One of the more popular FTP Daemons for GNU/Linux, FreeBSD and other Un*ces. One of its best features is its configuration. It uses Apache-like directives which are almost intuitive in nature. It has virtually no exploits, unlike WU-FTPD and is licensed under the GPL.
Made by a dude nicknamed MacGyver.
http://www.proftpd.net