twittertyper
I unfortunately am not allowed to participate, but in anticipation of Yahoo!'s Hack Day 2008, I put together a little app I'll hopefully be able to port to YAP: twittertyper!
The concept is very simple. twittertyper displays the latest tweet from Twitter. To read the next one, first type out the tweet. The text is highlighted as you go. If you come across a character your keyboard (or operating system) won't let you type, just press Esc to move on to the next character.
twittertyper currently just pulls in from the public timeline; no authentication is supported to pull from your timeline (maybe in a future version). This mini-app is built on YUI. Source code (uncompressed) is free to peruse.
Note: If you use Twitter, I'm sure you're used to it being down. Errors happen often, but twittertyper attempts to handle them somewhat gracefully. Usually a page reload should suffice.