BackupPC is an open source (free!), enterprise class, disk based, backup & recovery solution that can be used to backup all the Windows, Mac OS X, Linux, and UNIX computers on your network.
Why backup to disk instead of tape?

• Disk is cheap. With the new 500GB SATA drives, its really easy to put together a backup server with 1+ TB of storage for very little money.
• Disk is fast. Backing up data to disk is much faster than backing up data to tape.
• No tapes to swap. Enough said. I hate swapping tapes.
• Reliability. What good is a backup if you can’t use it? If configured correctly, a Linux server with Disks in an appropriate RAID configuration is an extremely reliable way to store backups.
• Keep lots of file versions. Depending on the amount of free disk, its easy to keep lots of versions of your backups in an easy access spot. Want to login and restore a copy of that file from 6 months ago? 3 months? 2 weeks? No problem.

An example:

I have a client who has a few office PCs, a local Linux file server, a FreeBSD firewall server, and an offsite FreeBSD web/email server that is colocated 500 km away. We installed BackupPC on the Linux file server and it now backs up all the local PCs, the firewall, the Linux File Server, and the FreeBSD servers. BackupPC connects to the Windows computers using Samba (Rsync is an option) and backs up the FreeBSD servers using Rsync to save internet bandwidth. We’ve done several restores and the system has saved us on more than one occasion due to system crashes, viruses, etc.

Off-site Backup

Storing backups off-site is an integral part of any backup solution to guard against fire, flood, etc. Installing BackupPC on-site should really be regarded as a part of a larger backup strategy. BackupPC really comes into its own if you can install it in an off-site location and then have it backup your data over a VPN connection back to your office. This requires a decent internet connection, but it is a great way to ensure that your data is protected in case of hardware failure.