BTSync

BTSync 2.3.8 was recently released for Synology DSM (and other OS's). Previous versions had serious issues with NAS units not hibernating but this version has fixed the problem (confirmed by myself). For newcomers, BTSync is like a personal Dropbox. You sync your folders between your machines aslong they're online (or in the same LAN). A nice feature here is that you can also share your folders encrypted which means you can in theory store your personal stuff at your friends house (as long he is running BTSync) and he/she won't be able to read your data. Anyway, many guides for BTSync today are outdated (sadly) so I recommend checking out https://getsync.com for latest information on how to use it.