This looks neat - Scratch is a "free programming tool that allows anyone to create their own animated stories, video games and interactive artworks".
The site is getting hammered right now as this story was on Digg and the BBC site but it looks interesting, especially if you have kids. Abby loves working on the computer - and especially likes creative programs like TuxPaint. I'm certainly going to check this out. The BBC article also mentions HacketyHack which calls itself "the Coder's Starter Kit". Its built around Ruby and appears targeted at slightly older kids than Scratch.
Remember the days of plugging in the old Commodore into the TV set for some late night monochromatic programming. Those were the days! :)