The day before the holiday weekend ended, while simply checking email, everything went a bit pear-shaped with my laptop. One moment we were browsing MacRumors while concurrently reading emails when it all went wrong. If we remember correctly, Microsoft Entourage gave us an error and requested to rebuild the database; a moment later the whole desktop flashed and began breaking up graphically. Usually a restart tidies everything up, but this time OS X's built-in protection would not allow startup to complete as a safety measure, requiring more serious measures. Fortunately, just before this happened I had cloned my drive a week earlier using Carbon Copy Cloner.
Honestly, we had no idea how important Carbon Copy Cloner would become in just a few days; we originally used it to clone our drive while replacing a 250gb internal with a faster and larger 500gb drive to migrate one drive to another. The old drive was slipped into a USB external case and worked perfectly as a boot up drive backup, allowing us to use a few diagnostic tools on the malfunctioning new drive (a bad directory file, thankfully not hardware). The process is as simple as a few button presses, choosing which drive will clone to another and then picking and choosing specific files to update if you want to forgo just having the whole drive updated each time.
We also use Time Machine, but we've found Apple's integrated backup utility as far from perfect (it really requires a dedicated external drive just for backup; deleting files manually is close to impossible). We prefer Carbon Copy Cloner, which is free to try/use with the option to donate, because of the options to define scheduling/frequency, while incrementally backing up only what you feel is required to be updated. Makes more sense than the "backup for dummies" options of Time Machine. And then there's also the very useful cloned bootable drive, which as noted before, makings doing diagnostics on a failing or ailing drive easier. If you are an OS X user who has dealt with hard drive issues (if not yet, you will be one day), own an external drive, add Carbon Copy Cloner to your toolbox...you will not regret it, especially when you most need it.