I have this dream, that one day our calendar that (usually) hangs on the kitchen wall at home will be replaced by an electronic version.
Then I would be able to view our home calendar from work, and using something like Outlook 2007, overlay my work calendar with our home one.
I'd prefer that the home calendar be secure, in that there would be restrictions as to who could view it (eg. I wouldn't want robbers seeing that we're out for the evening!)
Jon Udell outlines how far he's managed to get with sharing calendars between different systems (Outlook and Google in his case).
The final missing piece is to have some kind of flat-screen, light-weight PC that we can hang on the kitchen wall to replace the paper calendar. This is probably the tricky bit, as I'm guessing at the moment this would be pretty expensive.
I think it will happen eventually when components get cheaper, but we're not there yet.