BackWPup is a free plugin which allows you to back up your entire WordPress site (files and database). I personally choose to back up my sites into Dropbox, so this review will explain the process in that context, however the plugin allows you to choose from other services besides Dropbox.
Better Than The Rest
I have spent a considerate amount of time trying to find a good backup to online service plugin on WordPress. I used to use ‘Online Backup for WordPress’ which suddenly stopped working across my site several months ago. The main thing you want in a good backup plugin is reliability so that won’t do. I have also used ‘WordPress Backup to Dropbox’. The downside with this is that each backup overrides the previous backup for that site. I prefer to have several copies of backups per site, this way in case my previous backup is too recent, I will still have access to other backups that go further back in time. A couple other negatives with WordPress Backup to Dropbox was that the backup process itself was very slow and unreliable, and also the backups are not zipped/compressed which in my opinion makes things harder to manage.
BackWPup To The Rescue
Along comes BackWPup by MarketPress to answer all your problems (They also offer a pro version which I didn’t need – Let me know if any of you have had experience with it, and if so, what are your thoughts). I found the plugin to be extremely easy to use and also very fast. There plenty of customization options, like choosing files and folders to exclude from your backups, that I found handy. Bottom line, it was able to provide my with a seamless way to make sure that my WordPress sites were backed up and filed away safely within Dropbox. I can’t recommend it enough.