Obviously, your ongoing objectives and strategy will affect your choice.
g4u looks pretty cool as a disaster recovery mechanism. But then there's the issue of daily backups and incrementals. Couple it with BackupPC? For a one-off system that might work. To automate and set up regular procedures you might go to one of the other recommendations.
For Amanda, I like the quick start link on the wiki at Zmanda better than the 15 minute guide linked by chrism01. They also have a native Windows client now. You can find links to both at http://www.linuxquestions.org/bookmarks/tags/backup