I was impressed with AceWiki. It's one of several wiki projects out there that's attempting to semantically organize the information people enter.
It's still a work in progress, and has some limitations. For example, it only allows people to enter sentences that conform to a subset of English vocabulary and grammar.
However, I hope these take off. There's such a huge amount of free data out there (e.g. Wikipedia) and we can't create programs to reason over it because the content is too noisy.
