Simple application to watch some directory for file changes & perform some action (written in Haskell of course).
I used it to send files via Dropbox to my printer server, but there are many more possibilities. ;)
Of course cron would do the job, but it's not the point ;)
Moreover file size monitoring is implemented so the action will be called only after file size stays still for a while (and not immediately when the file appears in the directory).