For almost a decade the Rumpus FTP server has been an essential and unchanging part of my working life. It provides a lightning fast, easy-to-use and configure FTP server Mac OS X (Windows version is available).
It makes it easy for clients to send us files using any standard web browser, and they see a customized and branded interface that makes it look more professional. Employees access files using either a dedicated FTP client like Transmit or using the web interface, and then get files back to customers using a powerful drop ship feature. Developers typically access using an FTP client or WebDAV.
One of the things that makes this work so well is a great user management system – without adding more accounts to the OS we can have multiple accounts specific to the ftp service, with very granular control over what each can do and see and where they can go, There are has never once been a situation where an account could not be set up with exactly the desired access and privileges.
Another nice thing is that even though it offers a web interface it does not conflict with another apache web server on the same machine – you can run it alongside another webserver(s).
Lastly the support is amazing. There few times there have been issues (always the result of not seeing something in the documentation and/or painting ourselves into a corner by trying something a little flaky) the response from support has always been fast, courteous and very helpful.