Does Wolfram|Alpha have an API? if so, you could do a pretty cool question/answer thing.
erikwiffin: @tweetin why is the sky blue?
tweetin: @erikwiffin The sky's blue color is a result of the effect of Rayleigh scattering. Shorter-wavelength blue light is... http://bit.ly/3qaEo
tweet.in could be a searchable/rankable/commentable database of all the searches that it has performed.