Seagate has announced a 1.5 TB external drive, the world's highest capacity external drive (for the moment).
If you have any music, pictures, or movies on your computer, you MUST back them up or you risk losing them all.
There's an old adage that there's only two types of hard drives: those that have failed, and those that will fail. If your hard drive fails, it's highly unlikely you'll ever get any of that data back. Think of all the photos you'll lose and music and movies you'll have to re-rip/re-buy/re-steal.
The 1.5TB FreeAgent GoFlex portable drive has USB 3.0, which can transfer three times faster than USB 2.0 (as long as your computer has a USB 3.0 connection, of course). It still works with USB 2 and 1, just with slower transfer rates. You can buy a FireWire upgrade cable for $40, if your computer is so equipped.
What makes this drive portable is that it just needs the USB connection, there's no external power supply. So you can backup your desktop, laptop and then bring it to your parents computer and back up their pictures and music as well (or roomate/spouse/live-in hobo/etc.).
The 1.5 FreeAgent GoFlex is available now for PC and Mac in black, black and black for $249.