Microsoft Windows now ships with an integrated free backup software which can be accessed by clicking <Start>, <Accessories>, <System Tools>, and <Backup>.
Most Unix systems come with a plethora of backup software options, including dd, cpio, tar, and dump.
If the free and basic backup software included with your OS does not meet your needs, you may want to look at some of these more comprehensive free backup software packages.
Free Backup Software for Microsoft Windows
Cobian Backup
Cobian Backup is a multi-threaded program that can be used to schedule and backup your files and directories from their original location to other directories/drives in the same computer or other computer in your network. FTP backup is also supported in both directions (upload and download).
Cobian Backup exists in two different versions: application and service. The program uses very few resources and can be running on the background on your system, checking your backup schedule and executing your backups when necessary.
Cobian Backup is not an usual backup application: it only copies your files and folders in original or compressed mode to other destination, creating a security copy as a result. So Cobian Backup can be better described as a “Scheduler for security copies”.
Cobian Backup supports several methods of compression and strong encryption.
Freebyte Backup
Freebyte Backup is a freeware backup program for Windows 95/98/ME/NT/2000/XP. Freebyte Backup allows one to easily copy (and filter) a large number of files and directories from various sources into one backup directory.
It is possible to backup all files found in the specified set of input directories, or to have only certain file types copied. Files can be filtered according to file-extensions. E.g. you can specify that you want to backup all .doc, .rtf, .jpg, .bmp files, but none of the .exe, .dll and .txt files. You can very easily define new file extensions yourself to be added to the filter.
SyncBack Freeware
SyncBack Freeware is a freeware program that helps you easily backup and synchronize your files to: the same drive; a different drive or medium (CDRW, CompactFlash, etc); an FTP server; a Network; or a Zip archive.
Free Backup Software for Unix and Microsoft Windows
AMANDA
AMANDA, the Advanced Maryland Automatic Network Disk Archiver, is a backup system that allows the administrator of a LAN to set up a single master backup server to back up multiple hosts to a single large capacity tape drive.
AMANDA uses native dump and/or GNU tar facilities and can back up a large number of workstations running multiple versions of Unix. AMANDA can also use SAMBA to back up hosts running Microsoft Windows.
Bacula
Bacula is a set of computer programs that permit you (or the system administrator) to manage backup, recovery, and verification of computer data across a network of computers of different kinds.
In technical terms, Bacula is a network based backup program.
Bacula is relatively easy to use and efficient, while offering many advanced storage management features that make it easy to find and recover lost or damaged files.
afbackup
afbackup is a client-server backup system allowing many workstations to backup to a central server (simultaneously or serially).
Backups can be started remotely from the server or via cron jobs on the clients.
afbackup has been tested on Linux, FreeBSD, AIX, IRIX, Digital Unix (OSF1), Solaris and HP-UX. The afbackup client has also been tested on SunOS and OpenBSD.