Recommend full site backup plugins

I am looking for a simple to use (or well documented) plugin that will allow a newbie (me) to backup my full site (WP-files, themes & databases).

It needs to be completely free and would be best if it could be scheduled to do auto backups. I will soon be using MultiSite. Not sure if it needs to do anything different to support that, but I am happy for all sites to be backup up as one if needed.

I have found a few by searching, but am unsure which is best so wanted your opinions.

Cheers.