zFTPServer

zFTPServer, the free to use utility enhanced in a multi-threaded interface to enable swifter and safer file synchronization and transfer.
The reliable tool with power and capability is extensively useful for personal as well as commercial users. Enriched with advanced capabilities this tool provides all necessary FTP server features along with user specific transfer limits, real-time monitoring, virtual directories, and so on. The feature list can be summarized as; it supports virtual file system with capability to mount any disk drive or directories, supports strong SSL or TLS encryption systems, compatible with standard TCP/IP connection, allows remote administration of server, supports anti-hammering features that detects and blocks attempts for multiple connections, manages user groups and account, supports upload balancing, and much more.
zFTPServer also supports automatic server updates and is available in multiple languages.

Although being extremely simple to use, there exists an advanced configurations mode which should satisfy every need... All in all making it a fast, powerful and free FTP server with the following highlights:
Virtual filesystem: Possible to mount any disk drive or directories at anywhere within the home directory of a user or group. This makes it possible to for instance merge several directories so they seem as one.
SSL/TLS support: Very strong encryption support (up to 256 bits AES).
Automatic updates: The server will update automatically when a new version is available (optional).
Scripting friendly: The server can be controlled through a standard TCP/IP connection, making scripts very easy to develop (e.g. creating new accounts through php).
Remote administration: The server and graphical user interface is separated which easily enables remote maintenance of the server.
Being a system service: Built in WindowsNT / 2000 / XP / 2003 service support.
Ultrafast transfer speed: More than 11MByte/sec. average on 100MBit LAN, outperformes most of the "famous" windows ftp servers.
Passive mode host / ip option: Ability to specify a host name for a server with dynamic ip adress to use in passive mode, e.g. myserver.no-ip.com
Powerful user and group account management: Users and Groups may join multiple number of groups simultaneously.
Support for upload balancing: With the virtual filesystem users' uploads may end up where there is space.
Advanced IP-Access management: Access rights with respect to ip adresses or domain names may be specified, granting or denying access from specific locations.
Advanced Account expiration: Accounts can be expired after a specific criteria has been fullfilled. Criterias include expiration after a specific date, after a specified number of days/weeks/months has passed, number of downloads performed and more.