The most interesting and exciting new app I've seen this month (other than Twine of course!) is a new semantic search engine called True Knowledge. Go to their site and watch their screencast to see what the next generation of search is really going to look like.
True Knowledge is doing something very different from Twine -- whereas Twine is about helping individuals, groups and teams manage their private and shared knowledge, True Knowledge is about making a better public knowledgebase on the Web -- in a sense they are a better search engine combined with a better Wikipedia. They seem to overlap more with what is being done by natural language search companies like Powerset and companies working on public databases, such as Metaweb and Wikia.
I don't yet know whether True Knowledge is supporting W3C open-standards for the Semantic Web, but if they do, they will be well-positioned to become a very central service in the next phase of the Web. If they don't they will just be yet another silo of data -- but a very useful one at least. I personally hope they provide SPARQL API access at the very least. Congratulations to the team at True Knowledge! This is a very impressive piece of work.