If you’ve ever delved into the world of having your own web site, you will inevitably have a need to send and retrieve files from your server via FTP.
FTP is really (and I mean really) old and still widely used. While it’s true you can send or receive files from the command line in any OS, the GUI way of doing it is much easier because you get things like drag’n'drop, mass uploading or downloading with subdirectories with just a few clicks and so on.
Filezilla
Where to get it: http://filezilla-project.org/
Supported OSes: Windows, Mac OS X, Linux
Whether you’re using Windows, Mac OS X or Linux, Filezilla is a rock-solid reliable stable FTP client with many features and an easy-to-use interface. Most people if given the choice of which free FTP client to use would most likely opt to go with Filezilla first.
WinSCP
Where to get it: http://filezilla-project.org/
Supported OS: Windows
WinSCP has also proven itself to be stable and reliable. Its drawback is that it’s Windows-only but definitely gets the job done. If you’re a Windows user you may prefer this over Filezilla as the interface is a bit easier to understand.
Core FTP
Where to get it: http://www.coreftp.com/
Supported OS: Windows
Core FTP has many features with command line support, but its single largest drawback is that it looks terrible. In addition there is a small "nag" screen each time you start it. But it’s free so you really can’t complain.
Need more choices?
A list of many FTP clients (both free and paid) are available here.
What about the FireFTP extension, for Firefox. I use that all the time.
I’ve used Winscp for a while now. It has never failed me. I think every web site owner has some personal relationship with their ftp client.