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.
NouvaLinux backup and rescue is a live CD with some special tools for making backups and system recovery. The main tool is an application made by RyXéo (a free software company): a partclone GUI. Backup is Clonezilla compatible: you can make backups with NouvaLinux backup and restore them with Clonezilla.
SnaRSShE (Snapshots via Rsync in a Simple Shell Environment) is a simple, lightweight (both in size and system requirements) server data archiving package designed for secure and reliable archiving of critical data of defined network systems. The general idea was taken from the need to capture snapshots of data on a regular basis and have easy access to that data. Originally, the script handled alerting as well, but the author since recognized the sense in offloading the alerting to a separate system. This script is a front-end for rsync, which does the real work. SnaRSShE just creates the environment and manages the rotation of archives.
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.