FJAX is the lastest development in the FTP world - the principle is simple:-

A web-application uses FTP (universally available) to upload scripts and content
It then executes them on the remote server
Results are either left on the remote server or returned to the web-application

Uses range from 'FTP Search' by uploading a PHP script (this can do a full-text search on an FTP site in seconds compared with potentially hours by downloading each file to view it) to a very common blogging site which I refrain from naming here that uploads user files directly to their own server via FTP.

I throw open a challenge here for all and anyone to come up with the most novel application of FJAX!