Here's the situation: I work from home, so backing up the hundreds of GB on my work systems through a VPN connection to the main office just isn't feasible.
Solution: an external IDE drive with some backup software. It doesn't really solve the problem if, say, the house burned down, but it's far better than not having one at all.
But here's where the cool part comes in. I googled for free backup software, and came across a forum posting that mentioned the good program DiscWizard that comes with Seagate hard drives. I thought, "hey I've got a Seagate hard drive, why don't I have that program". Next stop -- Seagate's downloads page for DiscWizard.
I looked at the software requirements, and the only requirement to use it was that you had to have a Seagate drive. Which fortunately, I do (a 250 GB IDE drive I bought to replace 2 80 GB drives that I never got around to actually installing). The program does check, via the hardware report, that the drive is actually made by Seagate; otherwise it won't work (I tested this with another non-Seagate drive that I had lying around -- yes, I have a lot of hard drives just sitting around. I'm a hardware geek).
<shameless plug>I should point out that the last 3 drives I've bought (the 250 GB, and 2 320 GBs) have been Seagate -- they all carry a 5 year guarantee, and they're usually the best reviewed ones on the web, in terms of performance and reliability.</shameless plug>
After the program installed and identified that I had a proper Seagate drive installed, I was able to make a complete backup image of my 80 GB laptop. But more than that, I could then make incremental backups (rather than overwriting the entire 80 GB image over and over again), and coolest of all, I could mount the created backup image as a drive on my laptop, and access the files inside it. The image mount can be either read-only, or even read/write.
That's pretty useful stuff for free software.