The first line of defense for hardware health, in my opinion, is Cocktail. This little piece of shareware is great for routine maintenance (especially for those of us who forget to *not* let their computer go to sleep, allowing Panther to run diagnostics on its own!). I sleep better knowing this is on my hard drive at all times.
DiskWarrior is the tool I reach for next. I always carry this CD with me just in case I need to boot up from it and repair any directory damage. DiskWarrior is unique in that it creates a new directory, all sparkly and fresh.
It's also a good idea to keep your Panther CDs with you, just in case all else fails. I was once at a conference where a speaker (who should have known better) began downloading/installing an OS update during lunch break. When he saw that the update was going to take longer than he had, he stopped it. Is it any wonder his Mac refused to operate?! Luckily I had my Panther CDs and saved his ignorant little self because he really REALLY should have known better :)
Make a complete copy of your hard drive before leaving the Batcave with Mike Bombich's Carbon Copy Cloner. It's super easy, though it takes awhile. Run it before you go to bed the night before you leave. Not only will you sleep better knowing all your data is safe, but you'll be safe against theft; if your laptop gets stolen, you've got a complete backup at home.
I also use iCal to keep my family and friends apprised of my whereabouts (where is she *this* week?!). Apple's iCal lets me share my calendar out over the Internet. I also put my flight numbers in so that my Mom & Dad don't have a heartattack when the news reports that a plane has crashed. iCal also syncs with just about everything, like Palm PDAs (personal digital assistant), etc.