SmartFTP is my favourite FTP client. It's free for personal use, has a very nice Explorer-like interface (now with tabs), you can use drag and drop, secure connections (TLS and SSL). SmartFTP also offers support for Unicode/UTF8/MBCS, IPv6, and UPnP. Multiple FTP connections can be opened at the same time, and you can copy files from one remote host to another (FXP). Remote-host directory information is cached for future viewing, and FTP URLs are supported.
Pretty impressive for just 2.3 MB. This is arguably the most developed FTP client. You can even download a native x64 version.