Free Extensible FTP-server: The Administrators Dream
Reliability, performance, and ease-of-use
zFTPServer is a free FTP server offering best-of-breed solutions for security, reliability and flexibility. As a FTP server, following all relevant standards, zFTPServer offers a wide variety of standard and enterprise level features, such as strong encryption support, security certificates support and an extremely powerful user and group administrations. Although free, zFTPServer is completely clean from any annoying tag-alongs.

Robust architecture and cutting edge technology Heavily threaded, user friendly and secure; in designing zFTPServer, resource allocation (and deallocation), concurrency and reliability have guided the development effort and design from the start. In the continuous development our new extentions, essentially pushes the boundary of zFTPServer towards becoming a full fledged business integration server, while still retaining its performance, small resource footprint, and its roots as a free and able FTP server.

400.000 users and counting
zFTPServer have gained ground over a number of years and is currently used in enterprise level business critical applications as well as by home users across the globe.
News
2008-Q3   New extension available for purchase:
"Speed Scheduler"
2008-Q2   "Authentication Integration for Windows" now includes Windows user account impersonation.
2008-Q2   Development on SFTP extension initiated. With this extension zFTPServer will support not only FTPS (SSL/TLS) but also the SFTP (SSH) protocol.
2008-Q2   New extension available for purchase:
"Authentication Integration for Windows"
2008-Q2   New extension available for purchase:
"Events and Messages : Proactive"
2008-Q1   Windows Vista UAC compability testing has been started.
2007-Q4   New extension available for purchase:
"Events and Messages : Reactive"
Screenshots
Main window Configuration window - General Configuration window - Security Configuration window - SSL/TLS Configuration window - Logging to File Accounts window - Home Directory Accounts window - Restrictions
It's FREE for both personal and commercial use