BaGoMa backs up and restores the contents of a GMail account. It can restore all the labels (folder structure), as well as the flags (seen/read, flagged) of a message. It supports the use of any character in labels, including non-ASCII characters and "/" (the label hierarchy delimiter). BaGoMa is tuned to work specifically with GMail. Each message is only downloaded and saved once. Backup solutions that are designed to work with regular IMAP accounts will download each message multiple times (once per label) when used to back up a GMail account. This can significantly increase the bandwidth requirements and the amount of storage required for backup. Additionally, a faithful restoration of your GMail account might not be possible from such a backup.
twcbackup is easy-to-configure backup software with a graphical configuration tool. It supports multiple backup methods. Usually, the bfsync method is used, which maintains a backup pool of SHA1-hashed files which allows file-level duplication. Automatic deletion of old backups, backup of local data or remote machines via ssh/rsync (Linux machines) or smb/rsync (Windows machines), and replication of the backup repository are supported.
Shasplit takes a large data block, splits it into smaller parts, and puts those parts into an SHA-based content-addressed store. Reassembling those parts is a trivial "cat" invocation. Repeating parts (e.g., from previous split operations) are stored only once, which allows efficient incremental backups of whole LVM snapshots via Rsync. Shasplit shows its strengths on encrypted block devices, but might be useful for non-encrypted data, too.