We were on the 7 day with 3 days at the parks total and took over 1500 pictures! I could set my camera at the highest resolution (takes about 1 mb per picture) and not worry about missing anything. Each night, while DW was getting ready for dinner, I would download the memory stick(s) from the day to the laptop and when I got enough, I burned them right to a cd (let it work while we were at dinner or a show) so we wouldn't have been able to go without it.
They do make devices that are like a portable hard drive that you can upload your memory cards into (several mfgs., MindStor, Kanguru, etc) that are smaller than a laptop but you can't view your shots right away. They're $300 to $420 and range from 10 to 30gig.