I have been using the FireFTP XUL application for months now. It is a Firefox extension written by Mime Čuvalo that is a really good FTP client. And it's integrated with Firefox. Since then I was poking around on the Internet, looking actually for Notepad++ (the programmer's editor) on SourceForge. In one of my searches I found FileZilla. Now here is a real FTP client.
FireFTP was good, but it was unable to use SFTP (that I could find), so connecting to Web storage at the University of Minnesota, where I have 20MB of space, was not an option. They said to use WinSCP, but that didn't connect to my non-secure site. A dilemma, and I was using two programs to do two sites. Not very efficient.
Now that I have found FileZilla, though, I am very happy with it, and am going to continue using that instead of FireFTP. I'm still keeping the latter around just in case, but I don't plan to use it all that much.