Interarchy is a robust file-transfer client for Mac OS X.

It’s my favorite tool for performing non-scriptable SFTP transfers from a GUI environment. Two features which I find really useful are its "Auto Upload" feature (drop a file on the Interarchy Dock icon and it will load it to the correct folder on the remote server, based on its location on the local file system) and its advanced mirroring engine which saves me a lot of work whenever I have to perform a Movable Type upgrade (which basically amounts to a full reinstall).

It has many, many other features, almost all of which are entirely uninteresting to me. But the excellent mirroring and Auto Upload implementation alone make this product worth having.