Essential camera gear for a round the world trip?

Because, as you will discover, weight is a major issue, you need to figure out what you want to shoot and haul only as much gear as is necessary.

Personally, I'd ask myself if I really need anything beyond one DSLR and one lens. I'd pretty much bet the mortgage that 90% of your shots will be in the 30-60mm range, so teaming up a D40X with Nikkor's excellent 18-70 would more than do the job.

If both travellers absolutely have to have their own camera, get another D40X and a wide angle lens such as Sigma's 10-20 or, if budget allows, Nikon's 12-24.

You could substitute the 85mm f1.8 for the above lens if you thought you'd be doing a lot of portrait-type shots.

As you suggest, I would not rely on a portable drive. Take a whole whack of 2GB cards -- 10 to start -- and have each person carry half in a secure spot. You can buy more if you need to.

I wouldn't bother with an external flash. Instead, I'd pack a small tabletop tripod and a remote control. This will let you shoot in very low light at reasonable ISO.

Of course, bring the battery charger. Don't bother with a spare battery if you're packing two bodies. If you're taking only one, add a spare battery anyway. You're not likely to run out of juice, but if the main battery fries, will you be able to locate a replacement?

Make sure your bag can be sealed against dust and sand -- you'd be surprised at how grubby some countries are. And if you're going to the tropics, definitely get some of those little silica packs which suck up moisture. I have had expensive lenses ruined by fungus.

Bottom line? Remember, you'll be humping this stuff on your backs possibly 12 hours at a time. My wife gets great travel shots from her 15-year-old $100 Olympus Stylus film camera, which weighs less than one Nikon lens. And she's not even a photography buff.

Lastly, I regret to say that I know nothing about geotagging so I can't make any recommendations in that regard.

Hope this helps, and have a great trip!

It looks like these guys have already given you some great advice on what to take. I agree with taking as many memory cards as you can, and put me down for a third vote on leaving the flash behind. You might want to look into Domke vests or jackets for all their pockets. You can store lots of things in those plastic bags that newspapers come in. Or ziploc bags. Plastic shopping bags can go from keeping shampoos and soaps from leaking in luggage, to protecting stuff in the rain, to keeping dirty clothes in your luggage.

If you'll be doing a lot of hiking, a monopod would be lighter than a tripod, and you can use it as a walking stick. You don't really need a tabletop tripod, as long as you have a camera bag with you to set your camera on. Even a wadded up jacket works as a table tripod in a pinch.

Use the time before you go to learn as much about the countries you will be visiting. Customs can be very strange in some places. Learn some phrases, too. They will appreciate that you're trying to learn their language.

Hey, and watch out for war-torn countries! Don't get yourself taken hostage anywhere. Enjoy your trip, and know that there are those of us here who are extremely jealous.

Wow. You've been a contributing member here for over a year and this is the first question you have asked! It deserves a great answer, so I would suggest that you take plenty of film. Buy prepaid film processing mailers so that you can drop them in the mail and have a box full of prints waiting for you when you get home.