I use basic rsync. You don't get any fancy GUI's or the ability to go back in time to various versions of files (at least with the way I use it), but it reliably creates backups that I can restore from and I can use it to backup/restore to/from most any machine as rsync is generally already installed or available for any platform.

I'll typically use a script containing something like:

rsync -avz --delete --exclude-from=/Users/Kevin/etc/backup.lst /Users/Kevin kevin@192.168.1.2:/backup

where backup.lst is a file containing a list of those files I don't want backed up (trash, caches, VMIs that are backed up separately, etc.)

Being a fan of the command line I use either rsync or rdiff-backup: http://rdiff-backup.nongnu.org/

No sexy gui but it does a great job of keeping diff backup sets day to day and letting you go back in time.

I haven't tried any of the others.

OpenSolaris supports a Time Machine like facility called "Time Slider". It uses ZFS' ability to do arbitrary number of snapshots and ties it into the GNOME interface. For more details and screenshots, see

http://blogs.sun.com/erwann/entry/zfs_on_the_desktop_zfs

At home I use BackupPC for my three Linux machines - it's pretty good at backing up several similar machines, although its use of hard links makes it a little special. At work we use Amanda with tapes, plus a weekly rdiff-backup with rdiffWeb for long term history.

The features of rdiff-backup seem good, but it requires that the remote machine also be running the same program, and that you trust the remote machine: it doesn't encrypt the backups.

Since I want to perform backups to a remote service that offers tons of disk space, but that I don't necessarily trust with my data indefinitely, I make use of duplicity. It uses the rsync protocol, but doesn't require the same program running at the other end, and it encrypts the archives with GnuPG.

I find rdiff-backup the correct tool for backing up my Linux workstations. I've started using it since 2007, and its helped me restore numerous machines as well.

On OSX, it seems like Time Machine is your best bet. On OpenSolaris, Time Slider, is a great GUI for ZFS. I know of people using ZFS snapshots to backup even MySQL databases, but I've not gone that far.

If you're after something "interesting", don't hesitate to read "Build your own MySQL Time Machine" - the presentation file is linked. This again, very MySQL specific (all thanks to the ZRM example :P)