Backing Up Data

How are you all backing up your data at home? Back in the day you used to be able to use slow tape drives to back up your data. As far as I know tape drives are no longer viable for home use because of capacity issues. I guess I could set up a raid 5 array, but that is kind of costly, especially considering the need for a controller and the like.

So how are most people backing up their home data? I write some key data to cd/dvd, but with several hundred gigs of information and data that is only practical for a small fraction of it. What should I be looking at in terms of doing a full back-up of all my data? Will it require me having additional hard disk storage equal to what I have and just do a straight copy? Or, is there a more efficient means for me to back up my home data?