Proper FTP Manager Required

I've created a web site system that a number of users use on their sites,
but I manage each individual site/system on my ISP's server.

Creating updates to this system was fine when I only had a few users, but
now its starting to become hard work uploading the required files to each
site (I use CuteFTP) so I wondered if you knew of an FTP app that would
allow me to automate the process.

I basically want to put a file or files in a local folder and then instruct
the app to auto-upload these files to the same places, but on each site. If
required, I can create the folder structure locally so that the app goes
through a set of folders locally and uploads them to the same places on the
sites.

Do you know of an app that can automate the process of uploading the same
files to certain directories across multiple FTP sites?