Would a jellybean iMac be much too large a footprint for this purpose? Probably.
However, that's how I have my tangerine DV currently in use. It's not literally in the kitchen, on my counter, but just a few feet away in the eating area, easily accessible from the kitchen, acting as a guest surfing/e-mail/iTunes jukebox station.
I'm betting any slot-loading iMac could be found for pretty cheap, if you had a 1-foot square area to devote to it?
The iBook thing sounds good too, but, like the iMac, the TV tuner thing is a no go without some sort of box, like EyeTV or Formac?