Over the years I decided to go with an external USB hard drive, but it is a pain remembering to connect it periodically, and if you leave it connected, it can get fried with the machine. Then I got a Macbook. My initial thought was to back it up to the Linux box over the network, and do backups there all in one place, but NFS connections on the laptop are somewhat unreliable, and I would often find the darn thing hung trying to do a disk write over the network.
I tried Time Machine, but I didn't like the way it worked. I don't want to keep all the old versions of stuff, I just want to be able to restore data. So I got a copy of SuperDuper! and it is very nice for backing up the laptop to an external disk. It's tech support is surly, but knowledgeable and I was happy with it for a number of years now. I also got a copy of Tuxera NTFS which lets my Macbook read/write external drives formatted for Windows. This makes interoperability of external drives between my Linux and Mac machines easier. Life was good.
Then I decided off-site backups would be a good idea in case the house floods, burns down, etc. I looked at some of the online backup solutions. The one I went with in the end was SafeSync. The reason I chose it was price - unlimited backup storage for $60/year. Since then the price has gone way up, so unless you have very little data to be backed up it's not a good solution (nor is any online backup I've seen). I have also some problems with them. They have a browser-based backup solution for non supported machines, but it doesn't work from a browser under Linux (so all I can back up is the Macbook). Their software insists on backing up everything under a folder - no exceptions. Which means if I want all my iTunes data backed up I also have to backup my podcasts, which means backing up many MB each day that I really don't need to. In addition, the Java app that performs backups is a resource hog. I don't think other online solutions are as bad, but I'm not willing to invest the money to find out.
So I found myself looking for a better backup solution that doesn't cost a fortune. Lifehacker suggests using multiple cloud services to get free online backups, but that is a headache, and still limited in storage size. I believe what I'm going to stick with is one of those fireproof safe boxes and keep my external drives in there. I know there are fireproof disk drives but they are more expensive than this solution, especially since I can use the fireproof safe for many drives.
Are you backed up? You should be!