Since Steve did the post How to Make a Vista Aux Display, I've been thinking about how to use my somewhat unused Tablet PC for a similar purpose. I had installed the Tablet PC Experience Pack and so I had the Ink Desktop to use as a notepad. I then added Konfabulator and I hid everything else on the desktop. This turns out to be a pretty cool bulletin board/information system. Here's a screen shot.
This can just sort of run and I can use the pen to make notes, or even pick it up to use for Web surfing or whatever. I was thinking about mounting in on the wall, but it's pretty convenient where it is now.