FTP Client

Note that web browsers provide read-only FTP access. And most html editors provide the ability to save a page directly to a remote ftp site. But sometimes you do need a pure FTP GUI.

On Windows, some ftp clients are:
www.smartftp.com (shareware, most complicated, but probably best)
http://filezilla.sourceforge.net/ (free open source)
http://www.ftpx.com/ (shareware, simplest)

On Mac OS:
http://rsug.itd.umich.edu/software/fugu/ (free open source)
http://cyberduck.ch/ (GPL)