The new Hitchhiker's Guide radio series has begun! Each episode will be available for listening on the web site for seven days after the Thursday evening (GMT) repeat broadcast. Listen to episode 1 now, before they take it down!
When you're done with that, check out the BBC's graphics-enhanced Flash remake of the Infocom text adventure.
That site is horrible! Somehow they managed to design it so you can't listen to the radio shows regardless of the browser you use. (I tried three different ones.)