My important programs are duplicated on a desktop and a laptop, the data is synced on both, and on an external drive connected to the router USB, and google drive, and skydrive.
Synctoy does this every evening, from the laptop. If it is not turned on it does it at next opportunity.
Has been reliable so far. 
Larger files like photos and video are backed up manually every month or so onto a second external drive.
I used to burn DVD backups but really can't be bothered as they now seem rather small, and external drives are cheap.
It wouldn't be that terrible if the photo and videos were somehow lost (house fire or something?) - as the better ones are uploaded on flickr or blogger, and video clips are on youtube.
Compared to the old days when everything was on paper or tape we have it covered really.

With the ever increasing capacity and shrinking physical size of drives it's already possible to put almost everything important ever saved to a our computers on a couple of flash drives. That trend will probably continue.
I noticed a 1TB flash drive the other day but it was £1000.
Soon that will be an everyday item.
http://www.amazon.co.uk/Kingston-DataTraveler-HyperX-1TB-DTHXP30/dp/B00E65QM8O