Mac program like WinSCP

CyberDuck is a nice file transfer program for the OS X. It will do SCP as well as sync your local folder with the remote.

Take a look at Transmit

With rsync and a little launchd fiddling, you can roll your own. Set up a launchd task that monitors your chosen file, and when it changes, runs rsync to copy things over to your server. If you're new to launchd, I recommend Lingon as a GUI.

Also, if you're only doing this for a few files and depending on how much access you have to the server, Dropbox may be a lot easier to set up.