There are threads about backup software already, for example see this (quite short one) here
, which suggests rsync. If you mean you want to backup (mysql) databases, you can take a dump of them and store those dumps. Incremental backups are rather easy with rsync; I'd say unless you have a big, complex setup of systems, a small script with rsync, run via crontab, is all you need. There are probably commercial solutions as well, which do this and that, but I don't see how they're worth the price for home use. If you're not home, you can always persuade your superiors to give some money for a ready-to-eat solution
Rsync would also be opensource, if you insist on it.
p.s. "best" is something that you define in your own situation; it is simply not possible for someone to tell you that product X is the best for you. It can be, but only you know.