I've carried on bike trips, but not tours, a Canon Digital Rebel, a Canon A85 Point and Shoot, a 30+ year old Konica TC and a nearly 30 year old Konica FC-1 (the Konicas are both film cameras). As a long time amateur photographer, I can give some general camera advice.

The way digital cameras are usually marketed is based on megapixel (MP) count, the requirement is based on the final image size. If your only posting to the web, a used 4MP camera is plenty, your also not going to cry if you break $50 camera the way you would a $5,000 camera. For 4x5 prints, 6MP is plenty, for 8x10 prints 10MP is plenty. Theoretically as the print size increases so does the required resolution, except for one other factor, so does the optimum viewing distance, which lessens the need for resolution. Buying a camera with more MP then you need just burns through memory cards faster.

There are generally 2 styles of digital cameras, point and shoot and single lens reflex. Point and shoot cameras can be very compact and easy to use. SLR type cameras tend to be more adjustable and can deal with difficult situations better, although these days they can often be put into automatic mode and used as easily as a point and shoot, they do take up more space and are generally heavier, especially if you carry additional lenses.

I think for touring, you generally want a camera that can accept standard (AA or AAA) batteries, cameras tend to have hefty power requirements, and you sometimes don't get as many chances to recharge batteries as you would like, so being able to buy a few non-rechargeable batteries can be helpful. It's the viewing screen that uses the power, so cameras that have viewfinders and allow you to turn the screen off, can have lower power requirements then ones that have only the screen.

Modern cameras generally use one of several types of replaceable memory cards, some cards are larger then others, none weigh much, forget any card that has a capacity lower then 500MB, and that really only applies to cameras of 8MP or less, more and you want at least a 1GB card. There are two ways to go, get enough cards that you can do your entire tour without downloading, or carry a laptop / alternate storage device, and download the camera on a regular basis. Libraries/internet cafes and such can be good for checking email and updating blogs, sometimes they do not let you plug stuff in though.The weight of an alternate storage device or laptop can be much more then the weight of a few memory cards.

I tend to stick to cameras made by camera companies, Canon, Nikon, Olympus, Pentax, Leica all make excellent products, with decent optics, some of the others may be okay, the Sony DSLRs are not bad (they are actually products of the former Konica-Minolta). I can't say about the others.