Dropbox is currently probably the best backup service out there. They support Linux, Mac and Windows with their own, very easy-to-use client program that completely automates the backup process. If you're not familiar with this service, read more from their website.

However, none of us want to send our data unencrypted to a remote server, especially since many of us are using the service in an enterprise environment. There is an easy solution: install the encfs package using your distribution's package management (eg. Synaptic) and create a new folder (let's call it "encrypted") under your Dropbox folder. Now you can do:

encfs /home/USER/Dropbox/encrypted /home/USER/Backup

Replace (obviously) "USER" with your username. I use the "paranoia" mode and my encryption key is actually random 100 characters long. Now you can rsync all your files to the folder /home/USER/Backup.

You can automate the encfs mounting, thus simplify using long keys like I do. Specify your encryption key to this source file (replace "YOUR-ENCRYPTION-KEY-HERE" with your own key) and compile the file with:

g++ dropbox-pw.cc -o dropbox-pw

Now you can use your script to automatically mount the encrypted folder:

encfs /home/USER/Dropbox/encrypted /home/USER/Backup --extpass=dropbox-pw

Then your script can verify the folder was mounted correctly and rsync everything, causing the Dropbox client program to upload all the files in the encrypted form to the remote server. The contents of the folder /home/USER/Dropbox/encrypted should be just garbled up filenames. Those are your files in the encrypted form now. Uploading my 25 GB of files took several days at first, but after that only the changed files are uploaded, which usually takes only minutes.

Quick and easy! I've upgraded the free 2 GB Dropbox offers to 50 GB. Quite a reasonable price actually, I think I paid only 99 $ (63 euros) for a whole year.