I use Acronis True Image Home 11 (though it is giving me fits currently!), and I also use Supper Flexible File Synchronizer to sync all data and media files that I consider important. All goes to an internal Seagate SATA HDD, and also to an external Western Digital My Book Essential USB drive. (Fortunately I am blessed with lots of HDD space -- both the Seagate internal and WD external drives are 500 GB, and all my working files are on another Seagate internal drive with 500 GB. My C: drive is a Western Digital internal SATA drive of 80 GB and it only has Windows XP and my installed programs).
On top of this I also subscribed to Mozy Online and backup all my data and media files to their servers. I currently have that set to update the online backup once daily. Mozy cost me about $45 for a year. I did use it recently when I had one of my hard drives fail. I didn't even need to use an Acronis image (fortunately!), but I simply logged on to Mozy and downloaded all that had been lost. Worked nicely! It takes a while to download - it's not a speed demon at all when restoring. But I just started it when I was going to bed and checked the following day and everything had downloaded - back into the exact same file and folder structure that it had been in. Nice!
I also have BackItUp, which a module that is a part of Nero Ultra. I do make a full backup of everything with that monthly.
All files that I consider critical -- those that I feel I would definitely regret losing - I burn to several DVDs weekly and store them out of my house. Sounds like a bit of overkill, but I have had to try and help too many friends who have lost data and seen the panic they are in. One friend thought he was backed up well - he kept a backup on an internal drive, plus one on an external drive, and even a set of DVDs weekly. Unfortunately there was a fire at this house. Very small - the firefighters said it was a smoldering fire, mostly inside the walls - electrical, I think. His office wasn't affected directly, but water they used got into the office ceiling and it collapsed onto his work station, and causing a shelf on the wall to fall. Computer was shot because of water, and the backup DVDs had been on the shelf and were also ruined. Weird things can happen! You can't be too careful - it all depends on how much you value the data on your machine.