There are several online backup services to choose from out there. Out of them all so far Mozy has been my service of choice. I just have the Mozy Home Free version which allows 2GB of storage. I know 2 GB is not a whole lot these days but I only back up MP3's of some of my guitar recordings. So far it seems to be enough. There are different backup plans you can purchase at varying prices. Let's take a look at the free software.
After installation you will need to set up how you want your backups to run.
Mozy has a simple explorer type interface that allows you to select individual files and folders for backup.
You can easily schedule the time and frequency of your backups.
There are also multiple options to choose from in determining how Mozy behaves.
When your all finished selecting the files and folders, there is a handy indicator that will show you how much of your free quota being used.