Syncany is an open-source cloud storage and filesharing application. It allows users to backup and share certain folders of their workstations using any kind of storage, e.g. FTP, Amazon S3 or Google Storage.
dvcs-autosync is a project to create an open source replacement for Dropbox/Wuala/Box.net/etc. based on distributed version control systems (DVCS). It offers nearly instantaneous mutual updates when a file is added or changed on one side but with the added benefit of (local, distributed) versioning and that it does not rely on a centralized service provider, but can be used with any DVCS hosting option including a completely separate server - your data remains your own.
Lsyncd uses rsync to synchronize local directories with a remote machine running rsyncd. Lsyncd watches multiple directories trees through inotify.
csync is a client only bidirectional file synchronizer. You can use csync for different things. The intention is to provide Roaming Home Directories for Linux but you can use it to synchronize your music collection or create a backup of a directory.
