From the Finder select Go, Connect To Server and enter ftp:// followed by the FTP site's name. The site will open in a Window on your Mac's desktop and you can drag and drop files just like any local folder.
Not sure what the equivalent is in MS Windows, but can you not go to a command prompt and type ftp <name of ftp server> then 'ls' will list the files, 'cd' will change directory and 'get' will get the files - before typing get, you need to type 'bin' if the file you are getting is binary rather than text.
fget followed by * will get all the files in a directory.
If you set prompt off before using fget then it won't keep asking you if you're sure you want that file.
put and fput will do exactly what you want.
Of course, you could just download FileZilla instead from
here. It is easy to use and it'll do everything short of make the tea - and it's 100% free. It'll even let you upload half a file and then resume to complete when you're ready.
ATB Rotf