We use and recommend CuteFTP, FileZilla or SmartFTP, as they are very stable and highly configurable. As we use these products ourselves, we can answer almost any question users ask about them, so if you believe you'll need help along the way, we highly suggest using any one of them.

There are other FTP products available in the market as well. If you are using a Macintosh, Fetch is probably the most popular FTP program available and is quite easy to use.