AbsoluteFTP is a nicely designed FTP client with a Windows Explorer-style interface.

AbsoluteFTP has a customizable, multi-window interface. Features of AbsoluteFTP include: drag and drop file transfers, customizable file types, the ability to perform transfers between two remote computers, the ability to copy files between directories on a remote FTP server, file transfer resuming, keep-alive functionality, and support for multiple simultaneous connections and transfers.