Summize presented a demo of their conversational search engine last night at the NY Tech Meetup. They also announced the launch of local search. The local search allows you to select a location (i.e. New York, Berlin, etc.) and a distance (i.e. 10 miles) and Summize will present only the conversations related to your search in that location.

The conversational search works with Twitter and can also provide an on-the-fly translation service so you can check out the latest conversations in other countries (like the China earthquake).

One note, the majority of conversations between friends still occurs on private services including AIM, Google Chat, Skype, etc. These services are not indexed by Summize.

Lastly, Summize offers an API which many of the most popular Twitter applications are using.