Sometimes, it pays to be non-OS driven.
AnyClient comes with standalone Windows, MacOSX, and linux apps for ftp. Actually it supports ftp, sftp, and webdav, but who’s counting. On top of that, there’s a java applet built right into the site that allows you to have access to an FTP client without having to install anything.
That’s pretty smooth when you’re in a bind and didn’t bother to haul your ftp client with you or you’re at a client’s place and need a file quick.