rsync is originally a file transfer program for Unix systems which provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand. This protocol has been ported to the Nokia S60 3rd Edition platform under the GPL license, allowing you to quickly upload and download files to and from your mobile device.

Before you run rsync you need to setup a configuration file telling rsync what directories to expose and other settings. This file will be in the C:\rsyncd directory. C:\ should be the drive letter assigned to the internal memory of your device. Inside the C:\rsyncd directory you need a configuration file rsyncd.conf where you can add the path to the files to be copied. More destination targets can be defined by giving their name in square brackets and a tab-indented path on the mobile device to that shared folder.

You can also choose to setup a sync relationship between your mobile device and desktop computer over a secure SSH connection.

Read complete setup and configuration instructions here. And you can download the sync client for Nokia S60 v3 here. Details on the sync protocol and examples can be found here.