xmedk

By taking indexed screenshots at set times of the teachers screen and having them uploaded to a web page, partcipants can succesfully attend a software oriented workshop. By applying timecodes that can also be inserted into the chat, all material stays synchronized. Example files can also be dropped into the folder and are shared via the internet.

rsync is a utility for synchronizing folders. it exists for all major operating systems, and is installed by default on OSX and Linux.

it's a command line terminal application, but not too hard to use.
there's a tutorial here:
everythinglinux.org/rsync/
main site:
samba.anu.edu.au/rsync/