As Uberfetus' writeup details, Fetch is a very good freeware FTP program available only for the Macintosh. Be aware that it is a deceptively powerful program, and you really can do some damage to a website if you're careless; as long as you watch what you're doing, everything should be okay.
A Very Quick Guide to Using Fetch
First, launch Fetch by double-clicking on the program icon. You will automatically be presented with a login window. Click "cancel" if you don't want to log in anywhere just yet. Once you're past the login screen, you can can go to the "Customize" top menu option and create shortcuts to preset the login window to automatically offer you any of many servers.
Once you've logged in to your server, you will be presented with a window full of files and folders. From here you can navigate by double-clicking on individual folders, and you can navigate up to higher directories by clicking on the pulldown menu directly above the file list. You can also navigate and create new directories (folders) from the "Directories" option of the top menu bar.
To upload and download files, you can either use the "Put File" and "Get File" buttons, or you can simply click and drag files to and from the desktop.
To upload a file from the desktop, click on the file icon and drag it into the Fetch window.
HTML files can be sent either in Automatic or Text mode, but should always be sent as Text, rather than Wrapped Text or any of the other formatting options. GIFs, JPEGs, PDFs and Excel files should be sent in Binary mode as Raw Data.
If you need to delete or rename a file or directory on the server, use the commands available in "Remote" on the top menu bar.