The "Eye-Fi" is a brilliantly simple device: a flash memory card with a Wi-Fi chip inside. As long as you remain in range of your computer's network, the Eye-Fi will automatically transfer any image you snap to your computer, where it can then be uploaded to the web manually or with the Eye-Fi software. (And it would be simple to set up some automatic uploading for instant uploads as soon as you take a snapshot if you wanted a custom solution.)
Gizmodo's Mark Wilson has a quick hands-on and says the Eye-Fi works "flawlessly" and doesn't have a noticeable drain on battery life. It's $100 for a 2GB version, which may not be a huge amount of flash memory, but considering it only really works as a buffer for later uploading that should suffice. If only they had a CF version, which would greatly simplify my Byzantine DSLR uploading rig for mobile reporting.
Product Page [Eye.fi]