Semantic search engine Powerset, which we've written about here before, has just launched its initial release. The current release is limited to indexing Wikipedia content, but it provides a great showcase for their technology and user experience.
For example, my search for "Alexander the Great" provided the following results page:
Here's the interesting part: If you look at the corresponding article in Wikipedia, you see a long text article, with biographical details in a table on the right. The Powerset results page adds to this by pulling out a great deal more data (listed as "Factz" in the results page) - such as territories conquered, cities founded and armies defeated. The Powerset engine has extracted this information from article.
Which brings us to the next question of interest: how will Google respond?