Cyberduck (by David Kocher) has been my favorite FTP/SFTP client for the Mac for a number of years. It essentially has a folder interface with which you can drag and drop files to or from your destination. It includes a bookmark system that is very easy to use. And most important, it supports SFTP, in addition to FTP, which is the defacto standard for copying files on the Internet. Recently I also discovered that Cyberduck has full DAV support which works great with the Oracle Beehive server at work.
Cyberduck is still available for free as an open source product. But it is also available on the Mac app store for $24.95. A great price considering what a great product this is.
Cyberduck - Mac App Store