Toby,
The type of portable computer you're looking for is termed a Netbook. These are basically very compact Laptops with display sizes ranging from about 8.9" to 11.1".
The Intel Atom Processors used in Netbooks don't have as much "horsepower" as those in full sized Laptops, so they wouldn't be as suitable for graphics applications or those requiring lots of processor power. However, they work well for E-mail, web browsing and other simple applications.
Some Netbooks are provided with Windows XP, some with Linux and some newer models with Vista Home. Some have built-in Memory Card readers and most have a Webcam and Wi-Fi capability. Most of the current models are provided with a 160GB hard drive, however some newer models have been upgraded to a 250 GB hard drive.
As you're not going to be travelling until next year and won't need the Netbook until then, I'd suggest waiting a few months before you buy one. That's a rapidly changing part of the portable computing market so there will undoubtedly be newer models coming in the next few months, with improved features. I suspect these will be a "hot" item at Christmas!
I'm also thinking of buying a Netbook before my next trip, and have been looking closely at the Toshiba NB-205. It's been getting good reviews on CNET and other sites.
Good luck and happy travels!