My husband and I are going to be traveling around the world (one stop per continent) this next April-June. I'd really like to be able to go with just one bag. My biggest question is, what bag would work best when I will be bringing my 15" Macbook Pro, and my digital SLR camera, along with an extra lens. I need a bag that will keep them safe, and will be good for my clothes, etc. too.

This is a tough one. The thickness of the camera equipment and the extra thickness of a good protective sleeve for the laptop will limit the types of bag you can take. We'll see what others think but I think a one-compartment bag like the MEI Voyageur or a bag like the Tom Bihn Aeronaut with large end pockets and a full-depth center compartment might work as well. A full-size SLR is a real challenge to pack. If you can keep it in your personal item bag, that would really help. The main bag's going to get heavy with the computer and camera.

Currently I have a camera bag backpack... but it doesn't allow very much extra room for anything else in the backpack. Should I keep it like that, the camera backpack as my personal item, or does anyone have a suggestion for a larger personal bag that would also have room for my camera stuff?

Here's an idea put together by Wired

http://howto.wired.com/wiki/Make_a_Stealth_Camera_Bag

Basically putting a couple grand in an expensive camera bag screams, steal my bag. build a little padding into a lowkey bag you have or from an army surplus shop and you can have a little more peace of mind.

Brad is right about how tricky a packing problem it is. But I think more because of the likely changes in weather from place to place. It might be possible to mail yourself additional clothes, or just buy locally when you get there (you'll blend in better anyway), donate it to someone homeless or the hotel staff afterwards,

I did this while on a two week trip through turkey, at one point we decided to stop taking public transportation and just travel on foot. This forced us to really evaluate everything in the bag, a small backpack (1,500 cc, 25L), out went the jeans, the benetton scarf, the wool sweater and two extra t-shirts. It was the best decision ever. We eventually decided to use the bus again, but the lightness of the pack was fantastically liberating.

And unless we had found ourselves in surprisingly different weather we could have travelled like that for months.

Have fun, sound like a good trip.

Dave and the other posters have a good point. Traveling with both a dSLR and a laptop will be cumbersome. I think you will need to make some choices.

I recently went to Italy on a business trip with my wife and then we spent about 6 days afterwards in the Lake Como area. So, while it wasn't a 'world trip', we faced some of the same problems of trying to one-bag the whole trip. For what I was doing, I found I could not, mainly because I had to bring there and back various promotional material (e.g., brochures) which were both bulky and reasonably heavy. We ended up checking one larger bag with the business oriented items (e.g., dressier shoes, flyers), and then had one carry on bag and one personal bag each with the really important or expensive items. If the checked bag didn't make it, we'd still be okay.

I agree with NOT using a dedicated camera type bag. While it might fit the laptop and dSLR, the bag will not be flexible enough for when you're just hiking about (e.g., out to dinner) and don't need the large, protective bulk of a dedicated camera bag with a laptop sleeve. My approach is to use a less obvious bag, and then to get a neoprene form fitting camera sleeve, Domke style foam wraps to bundle up any separate lens, and a sleeve for the laptop. This way, you can put them in the bag as needed for various excursions. And really, it's doubtful you'll be hauling your laptop around when visiting a museum or cafe!

I took my Nikon D300 with an 18-200 lens for maximum versatility, and brought along my Sigma 10-20 wide angle (very useful, although 18 mm on a cropped dSLR is decent for wide angle shots). I also packed a Gorilla (flexible) tripod, but admit a Pod bean bag might be better. I left the flash at home, but did bring a small, packable diffuser to soften the onboard flash. However, you're probably not going to want to reduce your camera kit to much less than this, so to save on space and weight, consider...

... leaving the 15" MacBook Pro at home, and getting something much smaller and portable. The current generation of Netbooks - while not great performers - are probably all you need, plus if it's damaged or lost, you will not have lost too much (e.g., MSI Wind, ACER Aspire One). If the Netbooks are too frustrating, even a smaller thinner laptop (e.g., MacBook Air, Fujitsu P1630) reduced bulk, which is sometimes worse than weight. Even a high end PDA or SmartPhone might do all you need.

In terms of bags, I use a Tom Bihn Aeronaut and the ID Messenger style bag. Good combination, tough wearing, and not too flashy but still good looking luggage.

Good luck with what you need to do, and have a great trip.

Take a look at Red Oxx's Safari-Beanos series:
http://www.redoxx.com/product_categories/1/products/33-safari-beanos-bag-pr4

They're sized for carry-on, but the shape will lend itself better to your elecronics and camera equipment. If you're going to carry the "personal item" as well, look at Red Oxx's Gator bag. It's a stand-up bag (literally) and seems perfect for camera equipment. The bottom is padded, which is a big help.

I had been hoping that the Gator would take my 15" MacBook, but alas, it doesn't. Well, at least it doesn't if I want to zip it closed. Hah.