I've looked for similar things, and been unable to find them.

For people like us who need these things, but don't want to do it alone their should be a sort of Wikipedia/Digg like distributed lexical database.

Everyone contributes data as it's acquired, and it is then verified by the users with a simple up/down vote for each child node.

The data could even be automatically acquired, and just manually verified as it is utilized.

Still an overwhelming task, but I think it would be worth it given all the fields that overlap with Natural Language Processing these days.