I’ve been using the WP-DBManager plugin for over a year now, and it has reliably sent a copy of my database to me each morning at 8am – straight to my inbox. When you look after a million WordPress sites (I think I look after about 15-20 at the moment) this plugin is a surefire lifesaver. Don’t forget you still need to backup you files on your server, and don’t forget to backup your uploads folder… some people always forget this one!
Anyway – a worthwhile install, and certainly adds to a bit of piece of mind in the fast moving world of WordPress!