First and foremost, you've got to be able to carry stuff with you and that means a backpack. Currently, there are two models I can recommend for different reasons:
I love my Brenthaven Apple backpack. It's big and has tons of zipper pouches, even one specifically for my iPod. It has very comfortable shoulder straps and is practically indestructible. There's even a removable, padded laptop pouch. The only downside to this pack, in my humble opinion, is that I can put *too* much stuff in it and it ends up feeling like a dead elephant on my back. Who knows how many people I've taken out in close quarters when this thing is fully loaded, weighing upwards of 50 pounds!
My second favorite backpack is the Shaun Jackson Laptrap. This thing is great because it can unfold and serve as a lap desk, and it's small enough to keep me from stuffing in the kitchen sink. The only downside I've found thus far is that the (removable) backpack straps are kinda tight and made out of a material that left a really nasty scratch on one of my leather coats! It's still a superb pack and I like carrying it as a shoulder bag.
When I'm on the road, I'm typically gone for weeks at a time; therefore, I tend to nest when I get to my hotel room. The very first thing I do is set up my iPod and Altec Lansing speakers. Nothing like a little Megadeth to make a girl feel at home :)
Speaking of iPods, my favorite case is simple: the one it came with! Honest, Apple's iPod Carrying Case with Belt Clip works great for me. Others that I've tried just don't feel as secure, and the clip on this one is big enough that if it falls off, chances are my *pants* have fallen off. It hasn't happened yet, thank the gods!
Another vital iPod accessory is obviously headphones, and again, Apple's EarBuds suit me just fine with one exception: you just have to try a pair of Griffin EarJams. You wouldn't believe the bass quality you get with these little clip-ons, and they stay in my ears better to boot.
Also consider grabbing up a Griffin iTalk. This little jewel let's you record voice memos straight into your iPod. It's even got an extra jack on top for plugging in an external mic, though I've found that sound quality through the built-in speak is very acceptable.
I also never leave home without my Apple iSight video camera. There's just nothing better for staying in touch with friends and family while away from home (broadband is a must though!). Pair it with Griffin's SightLight and you're all set. The SightLight does through a slight blue cast upon your glowing face, and does get a bit bright after a bit, but when you're low on light it's a great solution.
Lock that laptop up when you're out and about with a Kensington Microsaver Notebook Cable & Lock. While working at a conference or office, it's great for running to the little girl's room; just loop the cable around something you can't pick up and you don't have to pack everything when you run down the hall to freshen up!
My favorite digital camera for traveling is the Sony CyberShot U. It's purse-size, features an "instant on" function, and runs on two AAA batteries! I very rarely print photos, so this 2.1 megapixel camera is perfect for online use, and it's small enough to carry anywhere. It even takes short movies :)
To alleviate hauling yet another cable, I use a PCMCIA (or PC) card for transferring pictures from my camera to my laptop. This saves on camera battery life, plus the transfer rate is faster than that of a cable.
An extra hard drive for backups is also a great addition to your pack. I carry a Firewire, 10 gig drive by Smart Disk. It's small and doesn't require a power brick (it draws power right from my laptop). This is great for backing up files and also nabbing photos from friends at conferences like Macworld.
Blank CD-Rs (and even DVD-Rs) are also nice to have while traveling. I carry about 10 CDs with me and it never fails that by the time I reach home, they're all gone! They're great for backing up and sharing files, and your friends will love you for always having extras. Note: I never buy CD-RWs (rewriteable discs) on the off chance that I may be burning an audio CD for use in a car stereo. For some reason, they just don't work and to alleviate the possibility of confusion in haste, I only carry CD-Rs.
I always have at least one USB Flash drive (also called pen drives) with me. They're great for exchanging files at conferences. If you find yourself making a presentation, copy it onto your pen drive and you're ready to use another computer if yours crashes. I've used it several times at conferences when all speakers suddenly decide they need to have the same desktop picture (such as the conference logo).
Grab an AirPort Express and convert any ethernet connection to wireless. No longer am I tethered to the wall via those annoyingly short ethernet cable in hotels! It's also great for home use if you want to extend the signal of your base station, or of course, you can use it by itself. Note: Depending upon the hotel, you may have to turn authentication off in your email client in order to send mail.
Cables, cables, and more cables. Thank goodness there's retractable cables available from IOGEAR to save on space and weight! I carry three with me wherever I go: ethernet, phone, and Firewire. To date, I haven't found that USB needs to be on my list.
This one is obvious, though I wanted to put a plug in here for the joys of Bluetooth. My life is so much better now that I can sync my Sony Ericsson cell phone with my Mac. Each time I make a change in my address book in either place, it's updated when I sync. If you're renewing a cell phone contract, or in the market for a new phone, I urge you to consider one with Bluetooth.
Another joy of Bluetooth is my wireless headset. There are many models to choose from, and though they can be a tad pricey, they are *well* worth it. That's one less wire that I can get tangled up with headphones and Thor only knows what other electronics I have attached to me while running through the airport. Be sure to look for a model that uses the same charger as your cell phone, as it requires charging too. I find that I can talk for about 2 hours on a full charge.
There are also USB cell phone chargers available. This is really handy if you find yourself in an airport (DFW!) which, for some unknown reason, has virtually *no* plugs *anywhere*. Arg! What were they thinking?! Worse case scenario, you can get a little juice straight from your laptop with one of these babies.
If you're giving presentations, pick up a Keyspan Presentation Remote. That way you're not tethered to the podium or desk, and you can stalk around the stage. Stage stalking is fun :)
Save your wrist by having different methods of computing available to you. I carry a Bluetooth optical mouse for just this purpose. My wrist and thumb tend to cramp up with too much use of the trackpad, and this tiny little mouse is nice to switch to. Radtech's MiniMouse fits the bill perfectly.
Another great gadget to have while traveling is an EverywherePower by iGo. This lets you power your laptop, Palm pilot, cell phone, etc. from both a car and/or an airplane. Note: I used to think power was only available on planes in first class; however I've discovered it in coach on some flights by feeling around underneath the seat for a small, car-adapter-like port. Some carriers have it on alternating seat rows.