CrossFTP

CrossFTP is, as its name suggests, an FTP client with supports for FXP, SFTP, WebDav, MobileMe iDisk, and Amazon S3.

There are all sorts of things you can do directly from the program client, such as explore, compress and extract files and folders, search for information on Google with a single click, preview images without any noticeable difference in quality, and program transfers and syncs.

File transfers are very simple as well, since you can perform them traditionally, or by simply dragging objects between the various windows that you can have open simultaneously.

CrossFTP is a great FTP client with many features and interesting possibilities. The only problem is that you have to pay for it.